The UNIVARIATE Procedure

OUTPUT Statement

OUTPUT <OUT=SAS-data-set> < keyword1=names …keywordk=names > < percentile-options > ;

The OUTPUT statement saves statistics and BY variables in an output data set. When you use a BY statement, each observation in the output data set corresponds to one of the BY groups. Otherwise, the output data set contains only one observation.

You can use any number of OUTPUT statements in the UNIVARIATE procedure. Each OUTPUT statement creates a new data set to contain the statistics specified in that statement. You must use the VAR statement with the OUTPUT statement. The OUTPUT statement must contain a specification of the form keyword=names or the PCTLPTS= and PCTLPRE= options. See Example 4.7 and Example 4.8.

You can use the OUT= option to specify the name of the output data set:

OUT=SAS-data-set: identifies the output data set. If SAS-data-set does not exist, PROC UNIVARIATE creates it. If you omit OUT=, the data set is named DATAn, where n is the smallest integer that makes the name unique.

A keyword=names specification selects a statistic to be included in the output data set and gives the names of new variables that contain the statistic. Specify a keyword for each desired statistic, followed by an equal sign, followed by the names of the variables to contain the statistic. In the output data set, the first variable listed after a keyword in the OUTPUT statement contains the statistic for the first variable listed in the VAR statement, the second variable contains the statistic for the second variable in the VAR statement, and so on. If the list of names following the equal sign is shorter than the list of variables in the VAR statement, the procedure uses the names in the order in which the variables are listed in the VAR statement. The available keywords are listed in Table 4.14.

Table 4.14: Statistical Keywords

Keyword	Description
Descriptive Statistic Keywords
CSS	Corrected sum of squares
CV	Coefficient of variation
KURTOSIS \| KURT	Kurtosis
MAX	Largest value
MEAN	Sample mean
MIN	Smallest value
MODE	Most frequent value
N	Sample size
NMISS	Number of missing values
NOBS	Number of observations
RANGE	Range
SKEWNESS \| SKEW	Skewness
STD \| STDDEV	Standard deviation
STDMEAN \| STDERR	Standard error of the mean
SUM	Sum of the observations
SUMWGT	Sum of the weights
USS	Uncorrected sum of squares
VAR	Variance
Quantile Statistic Keywords
P1	1st percentile
P5	5th percentile
P10	10th percentile
Q1 \| P25	Lower quartile (25th percentile)
MEDIAN \| Q2 \| P50	Median (50th percentile)
Q3 \| P75	Upper quartile (75th percentile)
P90	90th percentile
P95	95th percentile
P99	99th percentile
QRANGE	Interquartile range (Q3–Q1)
Robust Statistic Keywords
GINI	Gini’s mean difference
MAD	Median absolute difference about the median
QN	$Q_ n$ , alternative to MAD
SN	$S_ n$ , alternative to MAD
STD_GINI	Gini’s standard deviation
STD_MAD	MAD standard deviation
STD_QN	$Q_ n$ standard deviation
STD_QRANGE	Interquartile range standard deviation
STD_SN	$S_ n$ standard deviation
Hypothesis Testing Keywords
MSIGN	Sign statistic
NORMALTEST	Test statistic for normality
SIGNRANK	Signed rank statistic
PROBM	Probability of a greater absolute value for the sign statistic
PROBN	Probability value for the test of normality
PROBS	Probability value for the signed rank test
PROBT	Probability value for the Student’s $t$ test
T	Statistic for the Student’s $t$ test

The UNIVARIATE procedure automatically computes the 1st, 5th, 10th, 25th, 50th, 75th, 90th, 95th, and 99th percentiles for the data. These can be saved in an output data set by using keyword=names specifications. You can request additional percentiles by using the PCTLPTS= option. The following percentile-options are related to these additional percentiles:

CIPCTLDF=(cipctl-options) CIQUANTDF=(cipctl-options)

requests distribution-free confidence limits for percentiles that are requested with the PCTLPTS= option. In other words, no specific parametric distribution such as the normal is assumed for the data. PROC UNIVARIATE uses order statistics (ranks) to compute the confidence limits as described by Hahn and Meeker (1991). This option does not apply if you use a WEIGHT statement. You can specify the following cipctl-options:

ALPHA= $\alpha$: specifies the level of significance $\alpha$ for $100(1-\alpha )\%$ confidence intervals. The value $\alpha$ must be between 0 and 1; the default value is 0.05, which results in 95% confidence intervals. The default value is the value of ALPHA= given in the PROC statement.
LOWERPRE=prefixes: specifies one or more prefixes that are used to create names for variables that contain the lower confidence limits. To save lower confidence limits for more than one analysis variable, specify a list of prefixes. The order of the prefixes corresponds to the order of the analysis variables in the VAR statement.
LOWERNAME=suffixes: specifies one or more suffixes that are used to create names for variables that contain the lower confidence limits. PROC UNIVARIATE creates a variable name by combining the LOWERPRE= value and suffix name. Because the suffixes are associated with the requested percentiles, list the suffixes in the same order as the PCTLPTS= percentiles.
TYPE=keyword: specifies the type of confidence limit, where keyword is LOWER, UPPER, SYMMETRIC, or ASYMMETRIC. The default value is SYMMETRIC.
UPPERPRE=prefixes: specifies one or more prefixes that are used to create names for variables that contain the upper confidence limits. To save upper confidence limits for more than one analysis variable, specify a list of prefixes. The order of the prefixes corresponds to the order of the analysis variables in the VAR statement.
UPPERNAME=suffixes: specifies one or more suffixes that are used to create names for variables that contain the upper confidence limits. PROC UNIVARIATE creates a variable name by combining the UPPERPRE= value and suffix name. Because the suffixes are associated with the requested percentiles, list the suffixes in the same order as the PCTLPTS= percentiles.

Note: See the entries for the PCTLPTS=, PCTLPRE=, and PCTLNAME= options for a detailed description of how variable names are created using prefixes, percentile values, and suffixes.

CIPCTLNORMAL=(cipctl-options) CIQUANTNORMAL=(cipctl-options)

requests confidence limits based on the assumption that the data are normally distributed for percentiles that are requested with the PCTLPTS= option. The computational method is described in Section 4.4.1 of Hahn and Meeker (1991) and uses the noncentral $t$ distribution as given by Odeh and Owen (1980). This option does not apply if you use a WEIGHT statement. You can specify the following cipctl-options:

ALPHA= $\alpha$: specifies the level of significance $\alpha$ for $100(1-\alpha )\%$ confidence intervals. The value $\alpha$ must be between 0 and 1; the default value is 0.05, which results in 95% confidence intervals. The default value is the value of ALPHA= given in the PROC statement.
LOWERPRE=prefixes: specifies one or more prefixes that are used to create names for variables that contain the lower confidence limits. To save lower confidence limits for more than one analysis variable, specify a list of prefixes. The order of the prefixes corresponds to the order of the analysis variables in the VAR statement.
LOWERNAME=suffixes: specifies one or more suffixes that are used to create names for variables that contain the lower confidence limits. PROC UNIVARIATE creates a variable name by combining the LOWERPRE= value and suffix name. Because the suffixes are associated with the requested percentiles, list the suffixes in the same order as the PCTLPTS= percentiles.
TYPE=keyword: specifies the type of confidence limit, where keyword is LOWER, UPPER, or TWOSIDED. The default is TWOSIDED.
UPPERPRE=prefixes: specifies one or more prefixes that are used to create names for variables that contain the upper confidence limits. To save upper confidence limits for more than one analysis variable, specify a list of prefixes. The order of the prefixes corresponds to the order of the analysis variables in the VAR statement.
UPPERNAME=suffixes: specifies one or more suffixes that are used to create names for variables that contain the upper confidence limits. PROC UNIVARIATE creates a variable name by combining the UPPERPRE= value and suffix name. Because the suffixes are associated with the requested percentiles, list the suffixes in the same order as the PCTLPTS= percentiles.

Note: See the entries for the PCTLPTS=, PCTLPRE=, and PCTLNAME= options for a detailed description of how variable names are created using prefixes, percentile values, and suffixes.

PCTLGROUP=BYSTAT | BYVAR

specifies the order in which variables that you request with the PCTLPTS= option are added to the OUT= data set when the VAR statement lists more than one analysis variable. By default (or if you specify PCTLGROUP=BYSTAT), all variables that are associated with a percentile value are created consecutively. If you specify PCTLGROUP=BYVAR, all variables that are associated with an analysis variable are created consecutively.

Consider the following statements:

proc univariate data=Score;
   var PreTest PostTest;
   output out=ByStat pctlpts=20 40 pctlpre=Pre_ Post_;
   output out=ByVar pctlgroup=byvar pctlpts=20 40 pctlpre=Pre_ Post_;
run;

The order of variables in the data set ByStat is Pre_20, Post_20, Pre_40, Post_40. The order of variables in the data set ByVar is Pre_20, Pre_40, Post_20, Post_40.

PCTLNAME=suffixes

specifies one or more suffixes to create the names for the variables that contain the PCTLPTS= percentiles. PROC UNIVARIATE creates a variable name by combining the PCTLPRE= value and suffix name. Because the suffix names are associated with the percentiles that are requested, list the suffix names in the same order as the PCTLPTS= percentiles. If you specify $n$ suffixes with the PCTLNAME= option and $m$ percentile values with the PCTLPTS= option where $m > n$ , the suffixes are used to name the first $n$ percentiles and the default names are used for the remaining $m - n$ percentiles. For example, consider the following statements:

proc univariate;
   var Length Width Height;
   output pctlpts  = 20 40
          pctlpre  = pl pw ph
          pctlname = twenty;
run;

The value twenty in the PCTLNAME= option is used for only the first percentile in the PCTLPTS= list. This suffix is appended to the values in the PCTLPRE= option to generate the new variable names pltwenty, pwtwenty, and phtwenty, which contain the 20th percentiles for Length, Width, and Height, respectively. Because a second PCTLNAME= suffix is not specified, variable names for the 40th percentiles for Length, Width, and Height are generated using the prefixes and percentile values. Thus, the output data set contains the variables pltwenty, pl40, pwtwenty, pw40, phtwenty, and ph40.

You must specify PCTLPRE= to supply prefix names for the variables that contain the PCTLPTS= percentiles.

If the number of PCTLNAME= values is fewer than the number of percentiles or if you omit PCTLNAME=, PROC UNIVARIATE uses the percentile as the suffix to create the name of the variable that contains the percentile. For an integer percentile, PROC UNIVARIATE uses the percentile. Otherwise, PROC UNIVARIATE truncates decimal values of percentiles to two decimal places and replaces the decimal point with an underscore.

If either the prefix and suffix name combination or the prefix and percentile name combination is longer than 32 characters, PROC UNIVARIATE truncates the prefix name so that the variable name is 32 characters.

PCTLNDEC=value

specifies the number of decimal places in percentile values that are incorporated into percentile variable names. The default value is 2. For example, the following statements create two output data sets, each containing one percentile variable. The variable in data set short is named pwid85_12, while the one in data set long is named pwid85_125.

proc univariate;
   var width;
   output out=short pctlpts=85.125 pctlpre=pwid;
   output out=long  pctlpts=85.125 pctlpre=pwid pctlndec=3;
run;

PCTLPRE=prefixes

specifies one or more prefixes to create the variable names for the variables that contain the PCTLPTS= percentiles. To save the same percentiles for more than one analysis variable, specify a list of prefixes. The order of the prefixes corresponds to the order of the analysis variables in the VAR statement. The PCTLPRE= and PCTLPTS= options must be used together.

The procedure generates new variable names by using the prefix and the percentile values. If the specified percentile is an integer, the variable name is simply the prefix followed by the value. If the specified value is not an integer, an underscore replaces the decimal point in the variable name, and decimal values are truncated to one decimal place. For example, the following statements create the variables pwid20, pwid33_3, pwid66_6, and pwid80 for the 20th, 33.33rd, 66.67th, and 80th percentiles of Width, respectively:

proc univariate noprint;
   var Width;
   output pctlpts=20 33.33 66.67 80 pctlpre=pwid;
run;

If you request percentiles for more than one variable, you should list prefixes in the same order in which the variables appear in the VAR statement. If combining the prefix and percentile value results in a name longer than 32 characters, the prefix is truncated so that the variable name is 32 characters.

PCTLPTS=percentiles

specifies one or more percentiles that are not automatically computed by the UNIVARIATE procedure. The PCTLPRE= and PCTLPTS= options must be used together. You can specify percentiles with an expression of the form start TO stop BY increment where start is a starting number, stop is an ending number, and increment is a number to increment by. The PCTLPTS= option generates additional percentiles and outputs them to a data set. These additional percentiles are not printed.

To compute the 50th, 95th, 97.5th, and 100th percentiles, submit the statement

output pctlpre=P_ pctlpts=50,95 to 100 by 2.5;

PROC UNIVARIATE computes the requested percentiles based on the method that you specify with the PCTLDEF= option in the PROC UNIVARIATE statement. You must use PCTLPRE=, and optionally PCTLNAME=, to specify variable names for the percentiles. For example, the following statements create an output data set named Pctls that contains the 20th and 40th percentiles of the analysis variables PreTest and PostTest:

proc univariate data=Score;
   var PreTest PostTest;
   output out=Pctls pctlpts=20 40 pctlpre=PreTest_ PostTest_
              pctlname=P20 P40;
run;

PROC UNIVARIATE saves the 20th and 40th percentiles for PreTest and PostTest in the variables PreTest_P20, PostTest_P20, PreTest_P40, and PostTest_P40.