SAS Frequently Asked Questions 

Can't find your question? Try checking our General FAQ page.

Installing, Customizing, Updating, Renewing

• See the pages on Installing, Customizing, Updating, Renewing for help with these topics.

• How do I update my SAS setinit (when my SAS has not yet expired)?
• How do I update my SAS setinit when my SAS/Windows has expired?

Reading/Writing Files

• Converting among SAS, SPSS and Stata
  • How do I convert among SAS, SPSS and Stata data files?
  • How do I move SAS files from Unix to Windows?
  • How do I read SPSS or Stata data files into SAS using Proc Import?
  • How do a read/convert a version 6 SAS files/format using SAS Version 9?
• Reading/writing data files
  • How do I read a data file that uses commas, tabs or spaces as delimiters between variables?
  • How do I write a data file that uses commas, tabs or spaces as delimiters between variables?
  • How do I read a delimited file with missing values?
  • How do I read a delimited file that has delimiters embedded in the data?
  • What are some common infile options for reading a raw data file?
  • How do I read raw data files compressed with gzip (.gz files) in SAS?
  • How do I read raw data via FTP in SAS?
  • How can I read multiple raw data files in SAS?
  • How do I read/write Excel files with .xls extensions in SAS?
  • How do I create an ASCII file from a sas data set using put statement?
  • How do I read multiple raw data files with the same structure in one data step?
  • How do I read in a character variable with varying length in a space delimited dataset?
  • How do I write out a fixed-format file in SAS?
• Transferring Files to/from other computer platforms
  • How do I transfer SAS data files from a PC to Unix? 
  • How do I transfer SAS data files from UNIX to a PC?  
• Reading/Writing SAS files with formats
  • How do I use a SAS data file with a format library?
  • How do I use a SAS data file when I don't have its format library?

Data Management

• General data management tasks
  • How do I use keep and drop efficiently?
  • How do I check that the same data input by two people are consistently entered?
  • How do I create a format out of a string variable?
  • How do I display information for all the SAS datasets in a directory?
  • How do I make unique anonymous ID variables for my data?
  • How do I standardize variables (make them have a mean of 0 and sd of 1)?
  • Is there a quick way to create dummy variables?  
  • How to access and use SAS ZIPCODE data files for the United States?
  • How can I recode my ID variable to be short and numeric?
  • Where can I find more functions to create new variables?
  • How can I reshape pairs data long to wide?
• Date and time related
  • How can I increment dates in SAS?
  • How do I create  time series variables using proc expand?
  • How can I create lag and lead variables in longitudinal data?
• Manipulating string variables
  • How can I find things in a character variable in SAS?
  • How can I get rid of extra spaces in a string variable?
  • How can I merge two files on address?
• Missing data issues
  • How can I see the number of missing values and patterns of missing values in my data file?
  • How do I specify types of missing values?
• Multilevel data issues
  • How can I create different kinds of centered variables in SAS?
  • How can I create an enumeration variable by groups?

Macro Variables and Macro Programs

• How can I get information to debug my SAS macro?
• How can I put a value from a data file to a macro variable?
• How do I  locate the SAS temporary work directory?

Output

• How can I create tables using proc tabulate?   
• How can I change the way variables are displayed in proc freq?  
• How can I direct the output from PC SAS to a file?  
• How can I export my SAS results to an Excel spreadsheet?
• How can I send SAS data/results to specific cells in an Excel spreadsheet?
• How can I include cells with zero counts in proc freq with the list option?
• How can I generate pdf and html files for my SAS output?

Statistics

• General
  • What are the differences between one-tailed and two-tailed tests?
  • Why do I get different values of kurtosis in SAS, Stata and SPSS?
• Analysis of variance
  • How can I do test of simple main effects?
  • How can I do ANOVA contrasts?
  • How can I perform a repeated measures ANOVA with proc mixed?
  • How can I minimize loss of data due to missing observations in a repeated measures ANOVA?
  • How can I test contrasts and interaction contrasts using the estimate statement?
• Linear regression
  • How do I interpret the parameter estimates for dummy variables in proc reg or proc glm?
  • How can I compare regression coefficients between two groups?
  • How can I compare regression coefficients across three (or more) groups?
  • How can I test differences in means using a cell means model?
  • How can I compute omega squared in SAS after proc glm?
  • How can I visualize interactions of continuous variables in multiple regression?
  • Why are Type III p-values different from the estimate p-values in proc glm?
• Logistic regression
  • How do I interpret odds ratios in logistic regression?
  • Why are my logistic results reversed?
  • How do I do a conditional logit model analysis in SAS?
  • How to estimate relative risk in SAS using proc genmod for common outcomes in cohort studies?
  • In Proc Logistic why aren't the coefficients consistent with the odds ratios?
  • How can I get "adjusted" predicted values from a logistic model in SAS?
  • How can I create contrasts with proc logistic?
• Multilevel
  • How can I perform mediation with multilevel data? (Method 2)
  • How do I run a random effect tobit model using nlmixed?
  • How do I run a random effect zero-inflated poisson model using nlmixed?
• Spatial statistics
  • How do I generate a variogram for spatial data in SAS?
  • How do I fit a variogram model to my spatial data in SAS using proc variogram?
  • How do I fit a variogram model to my spatial data in SAS using proc mixed?
  • How can I perform spatial Kriging in SAS?
  • How can I calculate Moran's I in SAS?
  • How do I model a spatially autocorrelated outcome?
• Survival analysis
  • How can I model repeated events survival analysis using proc phreg?
• Spline regression
  • When using Proc Transreg, what are the defaults with pspline?
  • When using Proc Transreg, what are the defaults with spline?
  • When using Proc Transreg, what are the defaults with bspline?
  • How can I find where to split a piecewise regression?
  • Given a knot location, how can I fit a piecewise model using Proc Transreg?
• Other statistics
  • Simple linear and nonlinear models using nlmixed.
  • From an OLS model to full mixed models using proc nlmixed.
  • How can I do zero-truncated count models using nlmixed?
  • Using the predict statement with nlmixed for predictions based on fixed and random effects.
  • How can I do path analysis in SAS?
  • Kappa statistic for variables with unequal ranges of scores
  • How can I compute Mahalanobis distance?
  • How can I obtain percentiles not automatically calculated?
  • How can I compute Durbin-Watson statistic and 1st order autocorrelation in time series data?
  • How do I compute tetrachoric correlations in SAS?
  • How can I perform a bivariate probit analysis using proc olim in SAS 9.1?
  • How do I test on Pearson correlation using Fisher's Z transformation in SAS 9.x?
  • How Do I perform Chow test in SAS using proc autoreg?
  • How can I test for equality of distribution?
  • How can I bootstrap estimates in SAS?
  • How can I generate a dose response curve in SAS?
• Survey
  • What types of weights do SAS, Stata and SPSS support?
  • Sample setups for commonly used survey data sets
  • Choosing the correct analysis for various survey designs, including
    • Simple random sampling
    • Stratified with certainty PSUs
    • One-stage cluster sampling
    • Probability proportional to size sampling
    • Stratified random sampling
    • Systematic sampling
    • Repeated systematic sampling
    • Stratified random sampling with allocation to strata
    • Other methods of estimation
      • Ratio estimation
      • Regression estimation
  • How can I take a simple random sample with or without replacement using proc surveyselect?
  • How can I take a stratified random sample using proc surveyselect?
• Multiple imputation
  • How can I test additional estimates in imputed dataset models?

Graphics

• How can I graph two (or more) groups using different symbols?
• How can I output a sequence of plots to a single webpage with a frame?
• What are some of the different symbols that I can use on a scatter plot?
• How can I move text on a plot?
• How can I view built-in templates for proc greplay?
• How can I use proc greplay to display multiple plots at the same time?
• How can I create an interactive 2-D scatter plot as an ActiveX object using ODS?
• How can I create an interactive 3-D scatter plot as an ActiveX object using ODS?
• How do I make a 3d Graph?
• How can I save a SAS graph to a gif file?
• How can I use the SAS output delivery system?
• How do I make a histogram with percentage on top of each bar?
• How do I create statistical graphs in SAS 9.1.3 without proc gplot?
• How can I visualize interactions of continuous variables in multiple regression?
• How can I visualize longitudinal data in SAS?
• How can I generate maps in SAS using an external shape file?
• How can I overlay density plots of different variables by group in SAS?

Other

• How does SAS compare with Stata and SPSS?