The Data Step

Subsetting IF

In a Data Step you can exclude some observations from the dataset with an if statement.

data tornados_1980s;
  infile FileName;
  input year city damages;
  * this limits input data to 1980s data;
  if 1980 <= year <= 1989;
run;
  • IF .. IN statement ```r if year in (1980, 1981, 1982); ```
  • AND, OR ```r if year = '1980' and city = 'Baltimore'; ```

    infile 'filename'

    In the data step, import data from a file with the infile command. ```r data tornados; infile 'tornados.dat'; input year city cost; run; ```

    Set

  • Use the set command to create a new data set from an already created set. The following creates a dataset of 1980s tornado data from the larger set of tornado data. ```r data tornados_1980s; set tornados; if 1980 <= year <= 1989; run; ```

    The PROC Step

    PROC SORT

  • The sort procedure, sorts data. You can sort by multiple fields.
  • Also you can print by a field. ```r proc sort data=tornados; by year city; proc print data=tornados; by year; run; ```

    PROC Univariate

    PROC Univariate generates descriptive statistics ```r proc univariate data=tornados; histogram year; run; ```

    PROC means

    Use proc means when you are only interested in basic descriptive statistics.

    PROC freq

  • generates tables for data in categories.

    PROC gplot

    ```r proc gplot data=tornados; plot year*cost; title 'Year by Cost tornados'; run; ```

    PROC corr

    compute the correlation

    ```r proc corr data=grades; var exam1 exam2 hwscore; run; ```

    PROC reg

  • p: prints obs, predicted, residuals
  • r: same as p, plus more
  • clm: 95% conf interval for mean of each obs
  • cli: 95% prediction intervals. ```r proc reg data=grades; model final=exam1 hwscore / p r cli clm; plot final*hwscore; run; ```

    Multiple Regression Analysis

    Variable Selection

    SAS has several methods for selecting variables ```r proc reg data=cdi; model y = x1-x8 /selection=rsquare best=1; model y = x1-x8 /selection=adjrsq best=5; model y = x1-x8 /selection=cp best=10; model y = x1-x8 /selection=forward slentry=0.10; model y = x1-x8 /selection=stepwise slentry=0.10 slstay=0.10; model y = x1-x8 /selection=backward slstay=0.10; run; ``` additional pages to try: <a href=http://www.ats.ucla.edu/stat/sas/modules/graph.htm>more sas