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The FREQ Procedure

Output Data Sets

PROC FREQ produces two types of output data sets that you can use with other statistical and reporting procedures. These data sets are produced as follows:

PROC FREQ does not display the output data sets. Use PROC PRINT, PROC REPORT, or any other SAS reporting tool to display an output data set.

Contents of the TABLES Statement Output Data Set

The OUT= option in the TABLES statement creates an output data set that contains one observation for each combination of the variable values (or table cell) in the last table request. By default, each observation contains the frequency and percentage for the table cell. When the input data set contains missing values, the output data set also contains an observation with the frequency of missing values. The output data set includes the following variables:

If you specify the OUTEXPECT and OUTPCT options in the TABLES statement, the output data set also contains expected frequencies and row, column, and table percentages, respectively. The additional variables are

When you submit the following statements

    proc freq;
       tables A A*B / out=D;
the output data set D contains frequencies and percentages for the last table request, A*B. If A has two levels (1 and 2), B has three levels (1,2, and 3), and no table cell count is zero or missing, the output data set D includes six observations, one for each combination of A and B. The first observation corresponds to A=1 and B=1; the second observation corresponds to A=1 and B=2; and so on. The data set includes the variables COUNT and PERCENT. The value of COUNT is the number of observations with the given combination of A and B values. The value of PERCENT is the percent of the total number of observations having that A and B combination.

When PROC FREQ combines different variable values into the same formatted level, the output data set contains the smallest internal value for the formatted level. For example, suppose a variable X has the values 1.1., 1.4, 1.7, 2.1, and 2.3. When you submit the statement

    format X 1.;
in a PROC FREQ step, the formatted levels listed in the frequency table for X are 1 and 2. If you create an output data set with the frequency counts, the internal values of X are 1.1 and 1.7. To report the internal values of X when you display the output data set, use a format of 3.1 with X.

Contents of the OUTPUT Statement Output Data Set

The OUTPUT statement creates a SAS data set containing the statistics that PROC FREQ computes for the last table request. You specify which statistics to store in the output data set. There is an observation with the specified statistics for each stratum or two-way table. If PROC FREQ computes summary statistics for a stratified table, the output data set also contains a summary observation with those statistics.

The OUTPUT data set can include the following variables.

The output data set also includes variables with the p-values and degrees of freedom, asymptotic standard error (ASE), or confidence limits when PROC FREQ computes these values for a specified statistic.

The variable names for the specified statistics in the output data set are the names of the options enclosed in underscores. PROC FREQ forms variable names for the corresponding p-values, degrees of freedom, or confidence limits by combining the name of the option with the appropriate prefix from the following list:
DF_degrees of freedom
E_asymptotic standard error (ASE)
L_lower confidence limit
U_upper confidence limit
E0_ASE under the null hypothesis
Z_standardized value
P2_two-sided p-value
PL_left-sided p-value
PR_right-sided p-value
XP_exact p-value
XP2_exact two-sided p-value
XPL_exact left-sided p-value
XPR_exact right-sided p-value
XL_exact lower confidence limit
XR_exact upper confidence limit

For example, variable names created for the Pearson chi-square, its degrees of freedom, its p-values are _PCHI_, DF_PCHI, and P_PCHI, respectively.

If the length of the prefix plus the statistic option exceeds eight characters, PROC FREQ truncates the option so that the name of the new variable is eight characters long.

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Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.