SAS Class Notes 2.0
Managing Data
1.0 SAS statements and procs in this unit
| keep | Keeps just named variables |
| drop | Drops named variables |
| set | Reads in named file(s). If more than one is
named, files are combined (stacked) |
| merge | Merges files |
2.0 Demonstration and Explanation
Example 2.1 - Honor's Thesis
Suppose we are undergraduates working on
our honors thesis and we wish to analyze just a subset of the hs1 data
file. In fact, we are studying "good readers" and just want to
focus on the students who had a reading score of 60 and higher. The
following shows how we can take the hs1 data file and make a separate
folder called honors and store a copy of our data which just has the
students with reading scores of 60 or higher.
data "c:\sas\honors\goodread";
set "c:\sas\hs1";
where (read >=60);
run;
proc means data="c:\sas\honors\goodread";
var read;
run;
Example 2.1, continued - keeping variables
Further suppose that our
data file had many many variables, say 2000 variables, but we only care about just
a handful of them, id female read and write. We can subset
our data file to keep just those variables as shown below.
data "c:\sas\honors\hskept";
set "c:\sas\honors\goodread";
keep id female read write;
run;
proc contents data="c:\sas\honors\hskept";
run;
Example 2.1, continued - dropping variables
Instead of wanting to keep
just a handful of variables, it is possible that we might want to get rid of
just a handful of variables in our data file. Below we show how we could
get rid of the variables ses and prog.
data "c:\sas\honors\hsdropped";
set "c:\sas\honors\goodread";
drop ses prog;
run;
proc contents data="c:\sas\honors\hsdropped";
run;
Example 2.2 - Master's Thesis
Now we have moved on to our master's
thesis. We have a folder called masters and we have been given a
file with the data for the males (called hsmale) and a file for the
females (called hsfemale). We need to combine these files together
to be able to analyze them, as shown below.
proc freq data="c:\sas\masters\hsmale";
tables female;
run;
proc freq data="c:\sas\masters\hsfemale";
tables female;
run;
data "c:\sas\masters\hsmasters";
set "c:\sas\masters\hsmale" "c:\sas\masters\hsfemale";
run;
proc freq data="c:\sas\masters\hsmasters";
tables female;
run;
Example 2.3 - Dissertation
Now we are working on our dissertation
and, as with our masters, we have been given two files. In this case, we
have a file that has all of the demographic information (called hsdem)
and a file with the test scores (called hstest), and we wish to merge
these files together. We show how to do this below.
proc print data="c:\sas\diss\hsdem"(obs=10);
run;
proc print data="c:\sas\diss\hstest"(obs=10);
run;
proc sort data="c:\sas\diss\hsdem" out=dem;
by id;
run;
proc sort data="c:\sas\diss\hstest" out=test;
by id;
run;
data "c:\sas\diss\hsdiss";
merge dem(in=one) test(in=two);
fromdem = one;
fromtest = two;
by id;
run;
proc print data="c:\sas\diss\hsdiss";
run;
proc print data="c:\sas\diss\hsdiss";
var id fromdem fromtest;
run;
proc freq data="c:\sas\diss\hsdiss";
tables fromdem*fromtest ;
run;
3.0 For More Information
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