What’s new in the FAQs?

FAQ:		What’s new?	Search the FAQs:
Last updated:		14 August 2008
Stata release:		10

Below are listed in reverse chronological order the additions to the online FAQs:

• Resources: When was Stata first released? When were later versions released? (Updated 14 August 2008)
  
  
• Resources: The Statalist FAQ (Updated 14 August 2008)
  
  
• Statistics: How do I fit a regression with interval constraints in Stata? (Updated 31 July 2008)
  
  
• Windows: How can I determine if my computer/operating system is 64-bit? (Updated 31 July 2008)
  
  
• Windows: How do I run Stata for Windows in batch mode? (Updated 02 July 2008)
  
  
• Statistics: Why do I get an error message when I try to run a repeated measures ANOVA? (Revised 29 May 2008)
  
  
• Macintosh: Why am I unable to copy graphs and tables from Stata into other applications? (Added 23 April 2008)
  
  
• Statistics: Is there a way to estimate a nonlinear combination with nlcom, when the error “expression too long” is displayed? (Addd 29 February 2008)
  
  
• Macintosh: Why does pressing Return after clicking on a variable in the Variables window sometimes output the variable twice? (Updated 26 February 2008)
  
  
• Resources: The Stata Journal FAQ (Updated 05 February 2008)
  
  
• Windows: Why do I get different results when running a ml procedure on Stata/SE and Stata/MP? (Added 30 January 2008)
  
  
• Statistics: How do I obtain percentiles for survey data? (Added 10 January 2008)
  
  
• Unix: Why does Stata 10’s graphical user interface perform so slowly on a Windows X server such as Hummingbird Exceed? (Added 13 December 2007)
  
  
• Unix: Do you have a version of Stata that runs in a computer cluster environment? (Added 13 November 2007)
  
  
• Unix: How do I prevent Stata(GUI) from crashing when executed remotely through X11 forwarding? (Added 29 October 2007)
  
  
• Windows: How do I load large datasets (>1Gb) under Windows? I receive an error r(909) saying “op. sys. refuses to provide memory”. (Updated 23 October 2007)
  
  
• Unix: I’m getting the warning message “Error converting format to locale encoding: Conversion from character set ‘UTF-8' to ‘646’ is not supported” when launching Stata. What does this mean? (Added 20 September 2007)
  
  
• Macintosh: Why does Stata crash when I open the Data Editor in Stata for Macintosh? (Added 10 September 2007)
  
  
• Data management: How can I apply the original value and variable labels after using the reshape command? (Added 30 August 2007)
  
  
• Data management: How do I set up an ODBC Data Source Name for Stata on Mac or Linux? (Updated 30 August 2007)
  
  
• Unix: Why is my output not aligned correctly on Stata for Unix? (Added 30 August 2007)
  
  
• Data management: How do I convert date variables into Stata elapsed time when the numbers run together, like “4151999”? (Updated 30 August 2007)
  
  
• Statistics: What is the relationship between baseline hazard and baseline hazard contribution? (Updated 24 August 2007)
  
  
• Statistics: What is the difference between random-effects and population-averaged estimators? (Updated 09 August 2007)
  
  
• Statistics: What is the difference between the linear and nonlinear methods that mfx uses? (Updated 09 August 2007)
  
  
• Statistics: Why does stsum sometimes report missing values for the percentiles for survival time? (Updated 09 August 2007)
  
  
• Statistics: How can the standard errors with the cluster option be smaller than those without the cluster option? (Updated 08 August 2007)
  
  
• Statistics: How do the ML estimation commands (e.g., logit and probit) compute the model chi-squared test when they estimate robust standard errors on clustered data? (Updated 08 August 2007)
  
  
• Statistics: Are the estimates produced by the probit and logit with the vce(cluster clustvar) option true maximum likelihood estimates?
  Is there a difference between the estimates produced by the svy: probit, with psu variable specified in svyset command, and probit, vce(cluster clustvar) (and, similarly, between svy: logit, with psu variable specified in svyset, and logit vce(cluster clustvar))? (Updated 08 August 2007)
  
  
• Statistics: Which references should I cite when using the vce(cluster clustvar) option to obtain Stata’s cluster-correlated robust estimate of variance? (Updated 07 August 2007)
  
  
• Statistics: How can I do a Chow test with the robust variance estimates, that is, after estimating with regress, robust? (Updated 07 August 2007)
  
  
• Statistics: Why do I obtain different results when executing xttobit on the same data in different sessions? (Updated 07 August 2007)
  
  
• Statistics: Must I use all of my exogenous variables as instruments when estimating instrumental variables regression? (Updated 27 July 2007)
  
  
• Statistics: How do I estimate recursive systems using a subset of available instruments? (Updated 26 July 2007)
  
  
• Windows: How do I load large datasets (>1Gb) under Windows? I receive an error r(909) saying “op. sys. refuses to provide memory”. (Updated 26 July 2007)
  
  
• Windows: Why do I receive an error when trying to run Stata/MP on my client machine? (Added 24 July 2007)
  
  
• Windows: Why do I receive the error “cannot open C:\Program Files\Stata10\STATA.LIC” on a Windows Vista machine? (Added 24 July 2007)
  
  
• Macintosh: Why does clicking on a variable in the Variables window or command in the Review window sometimes bring the window to the front? (Added 23 July 2007)
  
  
• Macintosh: Why does pressing Return after clicking on a variable in the Variables sometimes output the variable twice? (Added 23 July 2007)
  
  
• Macintosh: Why does right-clicking in the Variables or Review window sometimes clear multiple selections? (Added 23 July 2007)
  
  
• Statistics: When I run mfx, I am getting the warning message "warning: predict() expression unsuitable for standard error calculation. Option nose imposed". What does that mean? (Updated 23 July 2007)
  
  
• Statistics: How do I obtain bootstrapped standard errors with panel data? (Updated 20 July 2007)
  
  
• Statistics: My raw data contains evidence of both over-dispersion and “excess zeros”. Is a zero-inflated negative binomial model the only count data model that can account for both the over-dispersion and “excess-zeros”? (Updated 19 July)
  
  
• Statistics: How can I get confidence intervals for predicted probabilities after probit? (Updated 19 July 2007)
  
  
• Statistics: How can I obtain confidence intervals for predicted probabilities after logistic regression? (Updated 19 July 2007)
  
  
• Unix: Why do I receive the error "libtiff.so.3: cannot open" when trying to run Stata on a Linux machine? (Added 19 July 2007)
  
  
• Unix: How do I install Stata on a Unix/Linux machine? (Updated 03 July 2007)
  
  
• Unix: How do I run the dynamically linked version of Stata 10 on Linux? (Added 02 July 2007)
  
  
• Statistics: How do I estimate a nonlinear model using ml? (Updated 29 June 2007)
  
  
• Statistics: How can I generate a variable relating panel data to a reference panel? (Updated 28 June 2007)
  
  
• Resources: When was Stata first released? When were later versions released? (Updated 28 June 2007)
  
  
• Windows: Why do I receive the error "Unable to Locate DLL" upon launching Stata 10 on Windows 2000? (Added 27 June 2007)
  
  
• Unix: How do I install 64-bit AIX? (Added 25 June 2007)
  
  
• Resources: How do I cite the Stata software and FAQs? (Updated 19 June 2007)
  
  
• Graphics: How do I graph data onto a map with spmap (preferred)? (Added 04 May 2007)
  
  
• Statistics: How do I fit a linear regression with interval constraints in Stata? (Updated 13 April 2007)
  
  
• Statistics: How do I calculate row medians? (Added 26 March 2007)
  
  
• Data management: How do I calculate measures such as percent improved minus percent deteriorated? (Updated 26 March 2007)
  
  
• Data management: How can I identify first and last occurrences systematically in panel data? (Updated 26 March 2007)
  
  
• Data management: How can I drop spells of missing values at the beginning and end of panel data? (Updated 26 March 2007)
  
  
• Windows: Why do I receive the error r(603) when trying to update Stata running on Vista? (Added March 2007)
  
  
• Data management: How do I identify neighbors of points or areas on a rectangular grid in Stata? (Updated March 2007)
  
  
• Unix: How do I install Stata on a Unix/Linux machine? (Added 19 January 2007)
  
  
• Data management: How do I connect to a database by using a Stata plugin? (Updated 16 January 2007)
  
  
• Statistics: What meta-analysis features are available in Stata? (Added 08 January 2007)
  
  
• Windows: How do I load large datasets (>1Gb) under Windows? I receive an error r(909) saying "op. sys. refuses to provide memory". (Updated 11 December 2006)
  
  
• Data management: Why am I getting an error message that there is "insufficient disk space"? (Updated 11 December 2006)
  
  
• Data management: How do I connect to a database by using a Stata plugin? (Added 04 December 2006)
  
  
• Macintosh: How do I increase the memory allocated to Stata? (Added 08 November 2006)
  
  
• Statistics: Which references should I cite when using the cluster() option to obtain Stata's cluster-correlated robust estimate of variance? (Updated 06 November 2006)
  
  
• Data management: How do I identify neighbors of points or areas on a rectangular grid in Stata? (Updated November 2006)
  
  
• Statistics: How do I fit a linear regression with interval constraints in Stata? (Added 31 October 2006)
  
  
• Statistics: Why does xtgee sometimes report that convergence was not achieved? (Added 26 October 2006)
  
  
• Data management: How do I calculate the maximum or minimum seen so far in a sequence? (Added 19 October 2006)
  
  
• Data management: How do I calculate the number of distinct values seen so far? (Added 07 September 2006)
  
  
• Programming: Is there any way to get around the 70-option limit in Stata’s syntax command? (Added 15 August 2006)
  
  
• Graphics: What kind of graphs can I create in Stata? (Added 21 July 2006)
  
  
• Statistics: The results from estimation commands display only two-sided tests for the coefficients. How can I perform a one-sided test? (Added 20 July 2006)
  
  
• Unix: Why does Stata/MP on Solaris cause high CPU usage with the default value of environment variable SUNW_MP_THR_IDLE? (Added 20 July 2006)
  
  
• Mata: In Stata, can I use Mata matrices that are larger than Stata’s matsize? (Added 19 July 2006)
  
  
• Mata: How can I perform clustermat on a Mata matrix? (Added 19 July 2006)
  
  
• Mata: How can I send clustermat a matrix larger than the currently set matsize? (Added 19 July 2006)
  
  
• Windows: How do I run Stata remotely on my Windows-based PC? (Updated 11 July 2006)
  
  
• Windows: How can I automatically install Stata under Windows? (Added 10 July 2006)
  
  
• Statistics: If we change the order of cluster sampling and stratification when sampling the population, would the svyset command be different? (Added 03 May 2006)
  
  
• Graphics: How do I graph data onto a map with tmap? (Added 18 April 2006)
  
  
• Data management: How can I sample clusters, not individuals? (Added 04 April 2006)
  
  
• Resources: When was Stata first released? When were later versions released? (Added 21 February 2006)
  
  
• Resources: How do I share a new command with Stata users? (Added 15 February 2006)
  
  
• Windows: What kind of performance increase can I expect in going from 32-bit to 64-bit Stata? (Added 15 February 2006)
  
  
• Unix: What kind of performance increase can I expect in going from 32-bit to 64-bit Stata? (Added 15 February 2006)
  
  
• Data management: How do I deal with a report of repeated time values within panel? (Added 20 December 2005)
  
  
• Statistics: How do I obtain bootstrapped standard errors with panel data? (Added 29 November 2005)
  
  
• Graphics: How can I show scale breaks on graphs? (Updated 28 November 2005)
  
  
• Statistics: How do I estimate recursive systems using a subset of available instruments? (Added 22 November 2005)
  
  
• Data management: What are regular expressions and how can I use them in Stata? (Added 27 October 2005)
  
  
• Programming language: How can I use Stata to solve a system of nonlinear equations? (Updated 14 October 2005)
  
  
• Statistics: I am using a probit model, and mfx says that my marginal effect is greater than 1. Can that be correct? (Updated 12 October 2005)
  
  
• Windows: How does a Stata network license work? (Added 4 October 2005)
  
  
• Unix: How does a Stata network license work? (Added 4 October 2005)
  
  
• Mac: How does a Stata network license work? (Added 4 October 2005)
  
  
• Windows: What are the hardware requirements to run Stata? (Updated 4 October 2005)
  
  
• Unix: What are the hardware requirements to run Stata? (Updated 4 October 2005)
  
  
• Mac: What are the hardware requirements to run Stata? (Updated 4 October 2005)
  
  
• Mata: How can I calculate the Fourier coefficients of a discretely sampled function in Stata? (Added 4 October 2005)
  
  
• Data management: How can I create variables containing percent summaries? (Added 4 October 2005)
  
  
• Statistics: Can I use mfx on survey data with unweighted means? (Updated 30 September 2005)
  
  
• Statistics: Why should I not do a likelihood-ratio test after an ML estimation (e.g., logit, probit) with clustering or pweights? (Updated 30 September 2005)
  
  
• Graphics: How can I best get box plots on logarithmic scales? (Added 28 September 2005)
  
  
• Data management: How do I remove leading or trailing zeros from string variables? (Added 20 September 2005)
  
  
• Data management: How do I go through the groups of a variable in order of their first occurrence in the dataset? (Added 16 September 2005)
  
  
• Data management: How do I split a string variable into parts? (Updated 29 August 2005)
  
  
• Data management: Is there a way to tell Stata to try all values of a particular variable in a foreach statement without specifying them? (Updated 25 August 2005)
  
  
• Statistics: How large should the bootstrapped samples be relative to the total number of cases in the dataset? (Updated 15 August 2005)
  
  
• Statistics: Can you explain Chow tests? (Updated 10 August 2005)
  
  
• Statistics: How can I pool data (and perform Chow tests) in linear regression without constraining the residual variances to be equal? (Updated 03 August 2005)
  
  
• Statistics: Must I use all of my exogenous variables as instruments when estimating instrumental variables regression? (Updated 28 July 2005)
  
  
• Statistics: How can I compute the Chow test statistic? (Updated 28 July 2005)
  
  
• Statistics: How does Stata's implementation of GEE differ from other implementations? (Updated 25 July 2005)
  
  
• Statistics: Why do I obtain different results when executing xttobit on the same data in different sessions? (Updated 25 July 2005)
  
  
• Statistics: How do I get a bootstrap vector of results? (Updated 22 July 2005)
  
  
• Statistics: Is my boss correct in saying that the p-value given with a paired ttest should always be lower than the signrank? (Updated 22 July 2005)
  
  
• Statistics: Why does bootstrap give a warning message for non-eclass commands? (Updated 05 July 2005)
  
  
• Statistics: How do you test the equality of regression coefficients that are generated from two different regressions, estimated on two different samples? (Updated 01 July 2005)
  
  
• Windows: How can I determine if my computer/operating system is 64-bit? (Added 27 June 2005)
  
  
• Unix: How can I determine if my computer/operating system is 64-bit? (Added 27 June 2005)
  
  
• Macintosh: How can I determine if my computer/operating system is 64-bit? (Added 27 June 2005)
  
  
• Statistics: When I run mfx, I am getting the error message "Predict option unsuitable for marginal effects". What does that mean? (Updated 15 February 2005)
  
  
• Resources: The Statalist FAQ (Updated 06 December 2004)
  
  
• Data management: How do I export tables from Stata? (Added 03 December 2004)
  
  
• Windows: How do I install Stata for Windows on a network drive? (Updated 02 December 2004)
  
  
• Programming language: How do I process parallel lists in Stata 8? (Updated 01 December 2004)
  
  
• Statistics: Which references should I cite when using the cluster() option to obtain Stata's cluster-correlated robust estimate of variance? (Updated 11 November 2004)
  
  
• Web: What does the error r(?) mean when I try to connect to the Internet from within Stata? (Added 15 November 2004)
  
  
• Statistics: Why do I get an "unbalanced data" error message when I run nlogit? (Added 13 October 2004)
  
  
• Data management: How do I identify neighbors of points or areas on a rectangular grid in Stata? (Added 11 October 2004)
  
  
• Statistics: When I run mfx, I am getting the warning message "warning: Derivative missing. Try rescaling variable mpg". What does that mean? (Updated 17 September 2004)
  
  
• Statistics: I am using a model with interactions. How can I obtain marginal effects and their standard errors? (revised 13 August 2004)
  
  
• Statistics: How do you fit a model when the dependent variable is a proportion? (Updated 04 August 2004)
  
  
• Windows: What kind of machine should I purchase to make Stata run most effectively? (Added 30 July 2004)
  
  
• Data management: How do I count the number of distinct strings across a set of variables? (Added 30 July 2004)
  
  
• Windows: How do I get the Review and Variables windows to behave as they did before? (Added 30 July 2004)
  
  
• Statistics: I am using a model with interactions. How can I obtain marginal effects and their standard errors? (Added 18 May 2004)
  
  
• Statistics: When I use the eyex option of mfx, what is it actually computing and how does it relate to the coefficients of the loglinear model? (revised 18 May 2004)
  
  
• Data management: Can I use ODBC to write to an existing Excel file? (Added 08 April 2004)
  
  
• Statistics: I am using a probit model, and mfx says that my marginal effect is greater than 1. Can that be correct? (Added 06 April 2004)
  
  
• Statistics: I need to run mfx more than once on my dataset, and it's taking a long time. What can I do to make it run as fast as possible? (Added 06 April 2004)
  
  
• Statistics: Can I use mfx on survey data with unweighted means? (Added 06 April 2004)
  
  
• Statistics: I am using mfx after an estimation that has time-series operators in the independent variable list. How does mfx calculate the means of the independent variables? (Added 06 April 2004)
  
  
• Statistics: What is the eyex option of mfx actually computing? (Added 06 April 2004)
  
  
• Statistics: What does the nodrop option do in mfx? (Added 06 April 2004)
  
  
• Statistics: I am using mfx after an estimation that has an offset. How does mfx take that into account? (Added 06 April 2004)
  
  
• Statistics: Running mfx on my dataset takes a long time, and I am worried it may have crashed. How can I tell if it is still running? (Added 06 April 2004)
  
  
• Statistics: I am only interested in obtaining a few of the marginal effects for a few independent variables. How can I do that? (Added 06 April 2004)
  
  
• Statistics: When I run mfx, I am getting the warning message "warning: predict() expression unsuitable for standard error calculation. Option nose imposed". What does that mean? (Added 06 April 2004)
  
  
• Statistics: When I run mfx, I am getting the error message "Predict option unsuitable for marginal effects". What does that mean? (Added 06 April 2004)
  
  
• Statistics: When I run mfx, I am getting the warning message "warning: Derivative missing. Try rescaling variable mpg". What does that mean? (Added 24 March 2004)
  
  
• Statistics: What is the difference between the linear and nonlinear methods that mfx uses? (Added 24 March 2004)
  
  
• Statistics: How do I fit a bivariate probit model with partial observability and only one dependent variable? (Added 18 March 2004)
  
  
• Windows: How much memory does your computer need to run Stata for Windows? (Added 18 March 2004)
  
  
• Programming language: How do I assign multiple backslash characters to macros in Stata? (Added 18 March 2004)
  
  
• Data management: How do I identify leap years in Stata? (Added 23 January 2004)
  
  
• Data management: I am having problems with the reshape command. Can you give further guidance? (Updated 17 December 2003)
  
  
• Data management: Why do I get rows of missing data when I use infile? (Added 11 December 2003)
  
  
• Statistics: How do I test for panel-level heteroskedasticity and autocorrelation? (revised 09 December 2003)
  
  
• Statistics: How do I get the Euler–Mascheroni constant gamma = 0.57721 ... in Stata? (Added 02 December 2003)
  
  
• Statistics: How can I get an R-squared value when a Stata command does not supply one? (Added 24 September 2003)
  
  
• Data management: How can I replace missing values with previous or following nonmissing values or within sequences? (revised 19 September 2003)
  
  
• Statistics: How can you specify a term other than residual error as the denominator in a single degree-of-freedom F test after ANOVA? (revised 10 September 2003)
  
  
• Statistics: How can I form various tests comparing the different levels of a categorical variable after anova or regress? (revised 10 September 2003)
  
  
• Graphics: How can I get "nice" date labels on a graph? (revised 03 September 2003)
  
  
• Graphics: How can I get "nice" time of day labels on a graph? (revised 03 September 2003)
  
  
• Programming language: New Dialog FAQs section (Added 14 August 2003)
  
  
• Graphics: How can I get a histogram with varying bin widths? (Added 10 June 2003)
  
  
• Data management: How can I convert other packages' files to Stata format data files? (Added 14 May 2003)
  
  
• Programming language: What can you tell me about the Windows 98 operating system and dialogs? (Added 05 May 2003)
  
  
• Programming language: What can you tell me about using the .idlg files that are written by StataCorp and used in their dialogs? (Added 05 May 2003)
  
  
• Programming language: How can I take care of prerequisites in dialog boxes? (Added 05 May 2003)
  
  
• Programming language: What can you tell me about using the .idlg files that are written by StataCorp and used in their graphics dialogs? (Added 05 May 2003)
  
  
• Statistics: Why does xtgls not report an R-squared statistic? (Added 24 April 2003)
  
  
• Data management: How do I set up an ODBC Data Source Name for Stata on Mac or Linux? (Added 15 April 2003)
  
  
• Data management: Is there a way to tell Stata to try all values of a particular variable in a foreach statement without specifying them? (Added 7 April 2003)
  
  
• Data management: Why doesn't the destring command in Stata include an encode option? (revised 31 March 2003)
  
  
• Graphics: How can I get "nice" time of day labels on a graph? (Added 27 February 2003)
  
  
• Statistics: Why do I get an error message when I try to run a repeated measures ANOVA? (revised 20 February 2003)
  
  
• Data management: Why am I getting an error message that there is "insufficient disk space"? (Added 20 February 2003)
  
  
• Statistics: Which references should I cite when using the cluster() option to obtain Stata's cluster-correlated robust estimate of variance? (Added 12 February 2003)
  
  
• Statistics: How do I bootstrap a vector of results? (Added 11 February 2003)
  
  
• Resources: The Statalist FAQ (Updated 6 February 2003)
  
  
• Macintosh: Will Stata 8 for Macintosh run natively in OS X? (Updated 27 January 2003)
  
  
• Macintosh: Setting the default end-of-line delimiter (Added 27 January 2003)
  
  
• Macintosh: Executing Stata in background (batch) mode (Added 27 January 2003)
  
  
• Macintosh: Advanced starting of Stata (Added 27 January 2003)
  
  
• Macintosh: How do I increase the memory allocated to Stata? (Updated 27 January 2003)
  
  
• Macintosh: Stata is displaying graphs using the old scheme even though the setting is for the new scheme. (Added 27 January 2003)
  
  
• Data management: I want to calculate a variable containing weighted group summary statistics, but I do not want to collapse the data and egen does not support weights. How can I do this? (Added 24 January 2003)
  
  
• Statistics: For two-stage least squares (2SLS/IV/ivreg) estimates, why is the R-squared statistic not printed in some cases? For two-stage least squares (2SLS/IV/ivreg) estimates, why is the Model Sum of Squares sometimes negative? For three-stage least squares (3SLS/reg3) estimates, why are the R-squared and Model Sum of Squares sometimes negative? (Updated 20 January 2003)
  
  
• Data management: How do I deal with multiple responses? (Added 15 January 2003)
  
  
• Statistics: What are the differences between predict and adjust? (Added 25 September 2002)
  
  
• Data management: How can I collapse my dataset and keep the same variable labels? (Added 25 September 2002)
  
  
• Data management: How do I identify runs of consecutive observations in panel data? (Added 20 August 2002)
  
  
• Programming language: How do I signal that there are alternative types of arguments to program options? (Added 20 August 2002)
  
  
• Data management: How do I select a subset of observations using a complicated criterion? (Added 25 July 2002)
  
  
• Statistics: How can I generate a variable relating panel data to a reference panel? (Added 18 July 2002)
  
  
• Statistics: What do I do when one of the survey estimators returns an error message, "stratum with only one PSU detected"? (Added 12 July 2002)
  
  
• Statistics: Is there any difference between using tsset and iis and tis before xt commands? (Added 12 July 2002)
  
  
• Statistics: How can I calculate percentile ranks?
  How can I calculate plotting positions? (Added 10 July 2002)
  
  
• Data management: How can I generate a variable containing the last of several dates? (Added 14 June 2002)
  
  
• Graphics: How can I get "nice" date labels on a graph? (Added 11 June 2002)
  
  
• Data management: How can I save one or more parts of a large dataset? (Added 31 May 2002)
  
  
• Windows: Why will the new executable not work after I updated Stata? Why is the old executable (wstata.old) still running after I updated the executable? (Updated 17 May 2002)
  
  
• Data management: Each morning I have to set my memory size to, say, 20m. The default, 1m, is not sufficient for my data. Is there a way of changing the default setting? (Added 19 March 2002)
  
  
• Data management: How do I compute the number of distinct observations? (Added 28 February 2002)
  
  
• Statistics: Why do I sometimes get negative eigenvalues when using the pf and ipf options of factor? (Added 25 February 2002)
  
  
• Statistics: Why does the cumulative proportion of variance sometimes exceed 1 when using the pf and ipf options of factor? (Added 25 February 2002)
  
  
• Data management: How do I tabulate cumulative frequencies? (Added 25 February 2002)
  
  
• Statistics: How do I calculate least square means in Stata? (Added 14 February 2002)
  
  
• Statistics: How do I estimate a nonlinear model using ml? (Added 14 February 2002)
  
  
• Programming language: What is the difference between a release marker and a version number in an ado-file? (Added 25 January 2002)
  
  
• Windows: How can I convert a Stata graph to .wmf (Windows metafile) format and preserve the color? (Added 4 January 2002)
  
  
• Data management: How do you process very large datasets in Stata? (Added 3 January 2002)
  
  
• Statistics: Can you explain Chow tests? (Added 2 January 2002)
  
  
• Resources: I see references to the findit and ssc commands on Statalist, but my Stata does not recognize these commands. What should I do? (Added 17 December 2001)
  
  
• Windows: Why can't I click in Stata's Command Window in Windows 2000/XP? (Updated 12 December 2001)
  
  
• Statistics: How can I calculate moving averages for panel data? (Added 12 December 2001)
  
  
• Data management: How do you efficiently define group characteristics in your data in order to create subsets? (Added 05 December 2001)
  
  
• Statistics: How do I impose the restriction that rho is zero using the heckman command with full ml? (Added 29 November 2001)
  
  
• Unix: How do I display graphs while connected to a Unix machine from my Windows or Macintosh computer? (Updated 27 November 2001)
  
  
• Resources: The Statalist FAQ (Updated 27 November 2001)
  
  
• Statistics: How can I use Stata to calculate power by simulation? (Added 19 November 2001)
  
  
• Statistics: How large should the bootstrapped samples be relative to the number of cases in the dataset? (Added 16 November 2001)
  
  
• Statistics: How can I estimate correlations and their level of significance with survey data? (Added 15 November 2001)
  
  
• Data management: How do I list observations in a group that differ on a variable? (Added 7 November 2001)
  
  
• Graphics: How can I show scale breaks on graphs? (Added 2 November 2001)
  
  
• Statistics: How do I calculate values of the beta function? (Added 2 November 2001)
  
  
• Data management: I am having problems with the reshape command. Can you give further guidance? (Updated 2 November 2001)
  
  
• Data management: How do I split a string variable into parts? (Added 25 October 2001)
  
  
• Statistics: How do you specify the variance function in nbreg to coincide with Cameron and Trivedi's (Regression analysis of count data, page 62) NB1 and NB2 variance functions? (Added 23 October 2001)
  
  
• Statistics: What is the difference between the models fit using nbreg, dispersion(mean) and nbreg, dispersion(constant)? (Added 23 October 2001)
  
  
• Data management: How can I put the current date and time in my log files? (Updated 23 October 2001)
  
  
• Graphics: How do I make my graphs come out square? (Added 22 October 2001)
  
  
• Data management: How do I perform multiple operations on data records if a condition is met? (Added 22 October 2001)
  
  
• Statistics: What is the difference between ‘endogeneity’ and ‘sample selection bias’? (Added 16 October 2001)
  
  
• Data management: What is true and false in Stata? (Added 16 October 2001)
  
  
• Windows: How do I load large datasets (>1Gb) under Windows? I receive an error r(909) saying "op. sys. refuses to provide memory". (Added 11 October 2001)
  
  
• Statistics: What is the relationship between baseline hazard and baseline hazard contribution? (Added 11 October 2001)
  
  
• Data management: Stata is reading in my variables as string, whereas they should be numeric. What should I do? (Added 11 October 2001)
  
  
• Statistics: How can I calculate the pseudo R² for xtprobit? (Added 2 October 2001)
  
  
• Resources: The Statalist FAQ (Updated 27 September 2001)
  
  
• Statistics: Is it possible to include a constant term (intercept) in ordered probit model within Stata? What is the relationship between ordered probit and probit? (Added 20 September 2001)
  
  
• Unix: Why won't Stata allow large datasets even when I am using a 64-bit Irix machine? (Added 18 September 2001)
  
  
• Unix: The Stata 7 installation requires uncompress, but on Mandrake 8, uncompress is not installed. How do I install it? (Added 18 September 2001)
  
  
• Data management: I am having problems with the reshape command. Can you give further guidance? (Added 11 September 2001)
  
  
• Macintosh: Will Stata for Macintosh run natively in OS X? (Updated 28 August 2001)
  
  
• Statistics: How does one estimate a model when the dependent variable is a proportion? (Added 21 August 2001)
  
  
• Data management: Is there a way to tell Stata to try all values of a particular variable in a for statement without specifying them? (Added 16 August 2001)
  
  
• Statistics: Why does bs now give a warning message for non-eclass commands? (Added 16 August 2001)
  
  
• Statistics: Does Stata support any multiple comparison tests following two-way ANOVA? (Added 07 August 2001)
  
  
• Statistics: How can you specify a term other than residual error as the denominator in a single degree-of-freedom F test after ANOVA? (Added 07 August 2001)
  
  
• Data management: How do I perform element-by-element operations on matrices? (Added 27 July 2001)
  
  
• Data management: How do I produce a dataset based on all possible pairs of identifiers within each group? (Added 18 July 2001)
  
  
• Resources: The Stata Journal FAQ (Added 28 June 2001)
  
  
• Statistics: How do I test for panel-level heteroskedasticity? (Added 28 June 2001)
  
  
• Programming language: How can I use Stata to solve a system of nonlinear equations? (Added 28 June 2001)
  
  
• Data Management: How do I get information from Excel into Stata? (Updated 15 June 2001)
  
  
• Data management: How do I create variables summarizing for each individual properties of the other members of a group? (Added 22 May 2001)
  
  
• Statistics: I am only interested in obtaining a few of the marginal effects for a few independent variables. How can I do that? (Added 21 May 2001)
  
  
• Statistics: How does mfx calculate the marginal effects of dummy variables? (Added 21 May 2001)
  
  
• Statistics: When do I need to specify the nonlinear option with mfx? (Added 21 May 2001)
  
  
• Statistics: I am not interested in the standard errors of the marginal effects. Can mfx display only the marginal effects? (Added 21 May 2001)
  
  
• Data management: How many significant digits are there in a float? (Added 11 May 2001)
  
  
• Data management: Why does the mod(x,y) function sometimes give puzzling results? Why is mod(0.3,0.1) not equal to 0? (Added 25 April 2001)
  
  
• Programming language: Why does a program defined by an ado-file sometimes not work when given a string comparison? (Added 25 April 2001)
  
  
• Windows: Memory reference errors and Windows crashes (Added 19 April 2001)
  
  
• Statistics: How should I interpret changing quadchk results? (Added 19 April 2001)
  
  
• Data management: Why doesn't the destring command in Stata include an encode option? (Added 16 April 2001)
  
  
• Statistics: How do you test the equality of regression coefficients that are generated from two different regressions, estimated on two different samples? (Added 12 April 2001)
  
  
• Statistics: Where can I find a description of the various time-series operators? (Added 12 April 2001)
  
  
• Statistics: How do I get the correct variance–covariance matrix from the bs routine? (Added 12 April 2001)
  
  
• Macintosh: When will Stata for OS X be available, and how much will it cost? (Added 3 April 2001)
  
  
• Statistics: How do I obtain the standard error of the predicted probability with logistic regression analysis? (Added 22 March 2001)
  
  
• Statistics: How can I obtain the standard error of the regression with streg? (Added 12 March 2001)
  
  
• Statistics: How can I produce adjusted means after ANOVA? (Added 08 March 2001)
  
  
• Statistics: Why are observations that are noninformative about the dependent variable, but are known to be selected, excluded by heckman from the estimation sample? (Added 08 March 2001)
  
  
• Statistics: What are some of the small sample adjustments to the sandwich estimate of variance? (Added 08 March 2001)
  
  
• Statistics: Why do I obtain different results when executing xttobit on the same data in different sessions? (Added 08 March 2001)
  
  
• Statistics: What is the between estimator? (Added 08 March 2001)
  
  
• Programming language: How can I automatically execute certain commands every time I start Stata? (Added 08 March 2001)
  
  
• Programming language: Why do I get puzzling results with the for command and local or global macros? (Added 08 March 2001)
  
  
• Windows: How do I run Stata for Windows in batch mode? (Added 08 March 2001)
  
  
• Resources: How can I download and install the StataQuest menu additions to Stata 7? (Added 02 March 2001)
  
  
• Macintosh: My computer crashes during installation.
  I'm getting a "Type 1" or "Type 11" error. (Added 02 March 2001)
  
  
• Statistics: How do you compute marginal effects after ologit/oprobit/mlogit using mfx? (Added 07 February 2001)
  
  
• Statistics: How can I take random samples from an existing dataset? (Updated 11 December 2000)
  
  
• Resources: The Statalist FAQ (Updated 5 October 2000)
  
  
• Graphics: How can I create a pie or bar chart containing categorical data? (Added 30 August 2000)
  
  
• Data management: How can I replace missing values with previous or following nonmissing values? (Added 23 August 2000)
  
  
• Data management: Why can't I compare two values that I know are equal? (Added 27 July 2000)
  
  
• Statistics: Must I use all of my exogenous variables as instruments when estimating instrumental variables regression? (Added 21 July 2000)
  
  
• Graphics: How do I make a frequency plot using Stata? (Added 20 July 2000)
  
  
• Data management: How can I put the current date and time in my log files? (Added 28 June 2000)
  
  
• Data management: How can I replace an observation of a variable with a different observation for another variable? (Added 28 June 2000)
  
  
• Data management: Why do I get the error message "no room to add more observations"? (Added 28 June 2000)
  
  
• Programming: I have an if command in my program that only seems to evaluate the first observation, what's going on? (Added 28 June 2000)
  
  
• Windows: What hardware specifications does Stata recommend for my computer? (Added 28 June 2000)
  
  
• Windows: How do I install Stata on a Windows network? (Added 27 June 2000)
  
  
• Windows: How can I edit a Stata graph in MS Word? (Added 2 June 2000)
  
  
• Resources: The Statalist FAQ (Updated 24 May 2000)
  
  
• Windows: Clicking on large datasets (14 April 2000)
  
  
• Statistics: What are the divisors used in xtgee? (24 March 2000)
  
  
• Statistics: How are estimates of rho outside the bounds [-1,1] handled in the two-step Heckman estimator? (9 March 2000)
  
  
• Resources: The Statalist FAQ (Updated 9 March 2000)
  
  
• Windows: I just updated my executable but the old executable (wstata.old) is still running. (2 March 2000)
  
  
• Resources: How can I download and install the StataQuest menu additions to Stata? (23 February 2000)
  
  
• Statistics: Why do I get an error message when I try to run a repeated measures ANOVA? (23 February 2000)
  
  
• Data management: I cannot use the by command with the command I need. Is there anything I can do instead? (17 February 2000)
  
  
• Statistics: My raw data contains evidence of both over-dispersion and "excess zeros". Is a zero-inflated negative binomial model the only count data model that can account for both the over-dispersion and "excess-zeros"? (9 February 2000)
  
  
• Statistics: How do I interpret the Vuong statistic of a test between a negative binomial and a zero-inflated negative binomial model for count data? (9 February 2000)
  
  
• Statistics: How do I interpret the Vuong statistic of a test between a Poisson and a zero-inflated Poisson model for count data? (9 February 2000)
  
  
• Data management: Why am I getting a message that there is no room on my hard drive? (8 February 2000)
  
  
• Programming: Why does my do-file or ado-file produce different results every time I run it? (7 February 2000)
  
  
• Internet: How can I obtain update information from the Internet at work and put it on diskette to update my computer at home? (20 January 2000)
  
  
• Resources: The Statalist FAQ (Updated 14 January 2000)
  
  
• Statistics: How can I do logistic regression or multinomial logistic regression with grouped data? (Updated 14 January 2000)
  
  
• Data management: How do I create a variable that contains a repeating sequence of numbers? (22 December 1999)
  
  
• Data management: How do I convert date variables into Stata elapsed time when the numbers run together, like "4151999"? (22 December 1999)
  
  
• Graphics: How can I change the format of data for my axes? (14 December 1999)
  
  
• Statistics: How can I pool data (and perform Chow tests) in linear regression without constraining the residual variances to be equal? (10 December 1999)
  
  
• Programming: Why is post giving a syntax error? (3 December 1999)
  
  
• Programming: I coded 'a'^2 and got the wrong sign. Why? (3 December 1999)
  
  
• Programming: How do I remove collinear variables from a varlist (3 December 1999)
  
  
• Statistics: How can I estimate stepwise Cox models? (2 December 1999)
  
  
• Statistics: What is the delta method and how is it used to estimate the standard error of a transformed parameter? (2 December 1999)
  
  
• Statistics: How can I obtain the correlation matrix as a Stata matrix? (2 December 1999)
  
  
• Programming: How do I add an observation to a dataset when coding an ado-file? (2 December 1999)
  
  
• Data management: Is there a way to put leading zeros in output? (2 December 1999)
  
  
• Data management: How big will my dataset be? (2 December 1999)
  
  
• Data management: How do I create individual identifiers numbered from 1 upwards? (1 December 1999)
  
  
• Statistics: How can I estimate a fixed-effects regression with instrumental variables? (30 November 1999)
  
  
• Technical support: Contacting Stata Technical Support (Updated 19 November 1999)
  
  
• Statistics: Why does clogit sometimes report a coefficient but missing value for the standard error, confidence interval, etc.? (19 November 1999)
  
  
• Statistics: Why is there no intercept in the clogit model? (19 November 1999)
  
  
• Statistics: In clogit, why can't I use covariates that are constant within panel? (19 November 1999)
  
  
• Resources: New category (12 November 1999)
  
  
• Resources: How do I cite the Stata software and FAQs? (12 November 1999)
  
  
• Resources: How can I learn more about Stata? (12 November 1999)
  
  
• Resources: Are there courses on Stata? (12 November 1999)
  
  
• Resources: What are Stata NetCourses? (12 November 1999)
  
  
• Resources: Are there books on Stata? (12 November 1999)
  
  
• Resources: Are there Stata user groups or meetings? (12 November 1999)
  
  
• Data Management: How do I get information from Excel into Stata? (11 November 1999)
  
  
• Statistics: How do I convert my spell-type data into a survival dataset? How do I stset my spell-type data? (4 November 1999)
  
  
• Statistics: How do I analyze multiple failure-time data using Stata? (4 November 1999)
  
  
• Statistics: How do I test endogeneity? How do I perform a Durbin–Wu–Hausman test? (2 November 1999)
  
  
• Data management: How do I create a variable recording whether any member of a group (or all members of a group) possess some characteristic? (26 October 1999)
  
  
• Data management: How can I create a dataset (matrix) of means (other stats) of variables from the current dataset? (25 October 1999)
  
  
• Statistics: Why do stcox and cox sometimes produce missing standard errors? (21 October 1999)
  
  
• Statistics: How can I form various tests comparing the different levels of a categorical variable after anova or regress? (18 October 1999)
  
  
• Graphics: How many items can be identified in the legend? (18 October 1999)
  
  
• Statistics: How are the standard errors and confidence intervals computed for relative risk ratios (RRRs) by mlogit? (8 October 1999)
  
  
• Statistics: How are the standard errors and confidence intervals computed for odds ratios (ORs) by logistic? (8 October 1999)
  
  
• Statistics: How are the standard errors and confidence intervals computed for hazard ratios (HRs) by stcox and streg? (8 October 1999)
  
  
• Programming: Why do some nested for commands produce an error? (28 September 1999)
  
  
• Windows: How do I save a .wmf file in color? (15 September 1999)
  
  
• Statistics: How does xtgls differ from regression clustered with robust standard errors? (25 August 1999)
  
  
• Statistics: How can I convert Stata's parameterization of ordered probit and logistic models to one in which a constant is estimated? Why is there no constant term reported in ologit and oprobit? (25 August 1999)
  
  
• Windows: Stata will not save my preferences under Windows NT. How can I save my windows preferences in Windows NT? (17 August 1999)
  
  
• Unix: How do I get around the "device busy" error while installing Stata on Solaris? (17 August 1999)
  
  
• Data management: How can I save a Stata 6 dataset so that it can be read in Stata 5? (10 August 1999)
  
  
• Statistics: How can I do a Chow test with the robust variance estimates, that is, after estimating with regress, robust? (23 July 1999)
  
  
• Statistics: Why does test sometimes produce chi-squared and other times F statistics? How are the chi-squared and F distributions related? (23 July 1999)
  
  
• Statistics: Why does stsum sometimes report missing values for the percentiles for survival time? (23 July 1999)
  
  
• Statistics: Why are there so many formulas for the inverse of Mills' ratio? What if I have censoring from above/below in my Heckman selection model? (26 May 1999)
  
  
• Internet: Why can my browser reach sites on the web but Stata can't? (27 April 1999)
  
  
• Statistics: For two-stage least squares (2SLS/IV/ivreg) estimates, why is the R-squared statistic not printed in some cases? For two-stage least squares (2SLS/IV/ivreg) estimates, why is the Model Sum of Squares sometimes negative? For three-stage least squares (3SLS/reg3) estimates, why are the R-squared and Model Sum of Squares sometimes negative? (20 April 1999)
  
  
• Windows: Help stopped working; how do I fix it? (19 April 1999)
  
  
• Statistics: Why do Stata's xtgee standard errors differ from those reported by SAS's PROC GENMOD? (19 April 1999)
  
  
• Statistics: How can I obtain confidence intervals for predicted probabilities after logistic regression? (19 April 1999)
  
  
• Technical support: New category (16 April 1999)
  
  
• Statistics: How can I obtain the correlation between the factors after an oblique rotation? (9 April 1999)
  
  
• Statistics: Why does xtreg with the mle option produce different results from xtreg with only the re option? (6 April 1999)
  
  
• Unix: How do I read data from a pipe? (15 March 1999)
  
  
• Data management: How do I accumulate the results of immediate commands? (12 March 1999)
  
  
• Unix: Why does the cpio command not work under Red Hat 5.2? (10 March 1999)
  
  
• Statistics: What is the difference between random-effects and population-averaged estimators? (13 January 1999)
  
  
• Statistics: What is the difference between biprobit/heckprob and the STB commands? (13 January 1999)
  
  
• Statistics: How can I fit an extreme value or gompit regression? (13 January 1999)
  
  
• Statistics: How does Stata's xtgee handle singletons with exchangeable correlation? (13 January 1999)
  
  
• Statistics: Where are the Wald tests for zinb that appear in the manual? (13 January 1999)
  
  
• Statistics: What are completely determined panels? (13 January 1999)
  
  
• Statistics: Can Stata estimate a Rasch model? (05 January 1999)
  
  
• Statistics: How can the standard errors with the cluster option be smaller than those without the cluster option? (24 July 1998)
  
  
• Statistics: Why does Weibull with entry and exit times produce different results from Weibull with duration? (8 July 1998)
  
  
• Data management: How do I implement SAS-like ARRAYs in Stata? (23 June 1998)
  
  
• Statistics: Why do Stata and SAS differ in the results that they report for the stratified Generalized Wilcoxon Test for time-to-event data? (4 June 1998)
  
  
• Statistics: How can I do logistic regression or multinomial logistic regression with grouped data? (4 June 1998)
  
  
• Statistics: How can I get predicted probabilities after svylogit, svyprobt, svymlog, svyolog, or svyoprob? (4 June 1998)
  
  
• Statistics: Is it possible to analyze survey data with two or more levels of clustering with the svy commands? (7 May 1998)
  
  
• Statistics: Is there a way in Stata to do stepwise regression with svylogit or any of the svy commands? (7 May 1998)
  
  
• Statistics: What are some of the problems with stepwise regression? (7 May 1998)
  
  
• Statistics: For two-stage least squares (2SLS) estimates, why is the R-squared statistic not printed in some cases? (Updated 28 April 1998)
  
  
• Statistics: Do the svy commands handle zero weight differently than non-svy commands do? (28 April 1998)
  
  
• Statistics: Why do Stata's cc and cci commands report different confidence intervals than Epi Info? (22 April 1998)
  
  
• Data management: The updated (28 Jan 1998) reshape command (21 April 1998)
  
  
• Data management: Why does reshape give a too-many-variables error? (21 April 1998)
  
  
• Graphics: How do I connect points only within groups? (23 March 1998)
  
  
• Windows: Why does Windows 95 seem to be swapping even though I haven't allocated all available memory to Stata? (19 February 1998)
  
  
• Statistics: What are the advantages of using the robust variance estimator over the standard maximum-likelihood variance estimator in logistic regression? (26 January 1998)
  
  
• Statistics: Are the estimates produced by the probit and logit with the cluster() option true maximum likelihood estimates? Is there a difference between the estimates produced by the svyprobt, psu() command and probit, cluster() (and, similarly, between svylogit, psu() and logit, cluster())? (18 December 1997)
  
  
• Graphics: How do I join paired points on a graph? (19 November 1997)
  
  
• Statistics: Why were the timings in the American Statistician (August 1997) review of the svy commands so slow? (23 October 1997)
  
  
• Statistics: How can there be an intercept in the fixed-effects model estimated by xtreg, fe? (23 October 1997)
  
  
• Data management: How do I identify duplicate observations in my data? (15 October 1997)
  
  
• Windows: Stata is crashing — Do you have a Logitech mouse? (12 September 1997)
  
  
• Windows: How do I create a Postscript (or EPS) file of my graphs? (27 August 1997)
  
  
• Statistics: Is it possible to analyze survey data with two or more levels of clustering with the svy commands? (15 August 1997)
  
  
• Statistics: Why should I not do a likelihood-ratio test after an ML estimation (e.g., logit and probit) with clustering or pweights? (15 August 1997)
  
  
• Statistics: How do the ML estimation commands (e.g., logit and probit) compute the model chi-squared test when they estimate robust standard errors on clustered data? (15 August 1997)
  
  
• Statistics: Can Stata's ML routine converge and produce answers that look good even when it shouldn't? (15 August 1997)
  
  
• Statistics: Why is it dangerous to use the robust cluster() option on areg (areg estimates the same fixed-effects model as xtreg, fe)? (18 July 1997)
  
  
• Unix: I am having trouble running Stata for Linux on my Linux computer. What is wrong? (18 July 1997)
  
  
• Data management: How can I produce a tabulation of a string variable that is listed in logical rather than alphabetical order? (4 July 1997)
  
  
• Statistics: Why does the goodness-of-fit chi-squared test reported by poisson change when the counts and exposures are grouped differently? (4 July 1997)
  
  
• Macintosh: My computer crashes during the installation. (10 June 1997)
  
  
• Windows: Stata is crashing -- Do you have a Toshiba laptop? (9 June 1997)
  
  
• Statistics: Why is the pseudo-R^2 for tobit negative or greater than one? (9 June 1997)
  
  
• Statistics: What is the effect of specifying aweights with regress or fit? (5 June 1997)
  
  
• Statistics: In ordered probit and logit, what are the cut points? (3 June 1997)
  
  
• Statistics: How can I compute the Chow test statistic? (30 May 1997)
  
  
• Statistics: Why do I get the message " outcome does not vary" when I perform a logistic or logit regression? (7 May 1997)
  
  
• Data Management: I am having trouble converting a SAS dataset to a Stata dataset using Stat/Transfer. What is wrong? (11 April 1997)
  
  
• Data Management: Why do I get the error "wrong number of values" when I use insheet to read data from Excel? (9 April 1997)
  
  
• Statistics: Why doesn't summarize accept pweights? What does summarize calculate when you use aweights? (31 March 1997)
  
  
• Data Management: How do I create dummy variables? (25 March 1997)
  
  
• Statistics: What is the difference between sts list and ltable? (24 March 1997)
  
  
• Statistics: Is my boss correct in saying that the p-value given with a paired ttest should always be lower than the signrank? (24 March 1997)
  
  
• Statistics: How does the anova command handle collinearity? (24 March 1997)
  
  
• Statistics: What is the pseudo R2 in the weibull output? (24 March 1997)
  
  
• Statistics: "I am running clogit and get the message Note: multiple positive outcomes within groups encountered. Is this something I should worry about or is this a normal message?" (24 March 1997)
  
  
• Statistics: Why can't a subject die at time 0? Why can't a subject enter and die at the same time in Cox? (18 March 1997)
  
  
• Windows: I just installed Stata 5.0 for Windows, but I used only two of the three disks. What is wrong? (18 March 1997)
  
  
• Programming: I just downloaded and installed an ado-file from an early STB (before STB-7), and I am having trouble running it. What's wrong? (18 March 1997)
  
  
• Data Management: Why is x>1000 true when x contains missing values? (18 March 1997)
  
  
• Data Management: Can I apply the label values command to more than one variable at once? I want to attach the same value labels to several variables. (18 March 1997)
  
  
• Data Management: How can I list, drop, and keep a consecutive set of variables without typing the names individually? (18 March 1997)
  
  
• Statistics: Is there a nested logit command? (18 March 1997)
  
  
• Statistics: For two-stage least squares (2SLS) estimates, why is the R-squared statistic not printed out in some cases? (17 March 1997)
  
  
• Data Management: Is there any direct way to save into a new variable the frequencies obtained by applying the command tabulate? (17 March 1997)
  
  
• Statistics: How do I estimate a Cox model with time-varying parameters? (25 February 1997)
  
  
• Statistics: Why don't the old huber results match the new robust versions? (25 February 1997)
  
  
• Statistics: How can I get robust standard errors for tobit? (25 February 1997)
  
  
• Statistics: What roles does the time variable play in xtgls? (25 February 1997)
  
  
• Statistics: How does Stata's implementation of GEE differ from other implementations? (25 February 1997)
  
  
• Statistics: Why must weights be constant within panel for xtgee? (25 February 1997)