Frequency Tables in SAS
Overview
Frequency tables are an excellent way to check the validity of your
data. Do the values you find for a variable fall within the range
of possibility. If not, then some form of measurement error or coding
error has occurred. For variables that use nominal or ordinal data
frequency tables are one of the key methods of analysis. SAS provides
two procedures for performing frequency tables, proc
univariate and proc freq.
Procedure Freq
Proc freq will produce a frequency table for each variable you list.
The basic format of this procedure is:
proc freq data=dataset;
tables variable-list;
run;
If you do not specify the tables keyword then all variables
will be done. This can (often does!) produce a large amount of output. For
a large number of cases using proc freq on interval or ratio variables may
not be the best approach to take and you should consider using
proc univariate.
Example 2. Using Proc Freq
Procedure Univariate
Proc univariate will produce a frequency table if directed to
by specifying the freq keyword in the procedure declaration.
Proc univariate will not analzye variables defined to be
of type character in the input keyword and is limited to
numeric values only. In addition, proc univariate will generate
a page with assorted statistics for each variable specified.
The statistics generated by proc univariate fall into three
categories, moments which provide statistics such as mean, variance,
etc.; quantiles which show the distribution of the values; and extremes
which highlight the highest and lowest observed values. The extremes
output is very helpful in identifying errors in your data for interval
or ratio variables.
The following code show the basic setup:
proc univariate data=dataset freq;
var variable-list;
run;
Using Proc Univariate with Freq Keyword
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Author - Jack Suess
UMBC University Computing Services
Created - 1/15/96