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The UNIVARIATE Procedure

Example 4.18 Binning a Histogram

This example, which is a continuation of Example 4.14, demonstrates various methods for binning a histogram. This example also illustrates how to save bin percentages in an OUTHISTOGRAM= data set.

The manufacturer from Example 4.14 now wants to enhance the histogram by using the ENDPOINTS= option to change the endpoints of the bins. The following statements create a histogram with bins that have end points 3.425 and 3.6 and width 0.025:


title 'Enhancing a Histogram';
ods select HistogramBins MyHist;
proc univariate data=Trans;
   histogram Thick / midpercents name='MyHist'
                     endpoints = 3.425 to 3.6 by .025;
run;

The ODS SELECT statement restricts the output to the "HistogramBins" table and the "MyHist" histogram; see the section ODS Table Names. The ENDPOINTS= option specifies the endpoints for the histogram bins. By default, if the ENDPOINTS= option is not specified, the automatic binning algorithm computes values for the midpoints of the bins. The MIDPERCENTS option requests a table of the midpoints of each histogram bin and the percent of the observations that fall in each bin. This table is displayed in Output 4.18.1; the histogram is displayed in Output 4.18.2. The NAME= option specifies a name for the histogram that can be used in the ODS SELECT statement.

Output 4.18.1 Table of Bin Percentages Requested with MIDPERCENTS Option
Enhancing a Histogram

The UNIVARIATE Procedure

Histogram Bins for
Thick
Bin
Minimum
Point
Observed
Percent
3.425 8.000
3.450 21.000
3.475 25.000
3.500 29.000
3.525 11.000
3.550 5.000
3.575 1.000

Output 4.18.2 Histogram with ENDPOINTS= Option
Histogram with ENDPOINTS= Option

The MIDPOINTS= option is an alternative to the ENDPOINTS= option for specifying histogram bins. The following statements create a histogram, shown in Output 4.18.3, which is similar to the one in Output 4.18.2:

title 'Enhancing a Histogram';
proc univariate data=Trans noprint;
   histogram Thick / midpoints    = 3.4375 to 3.5875 by .025
                     rtinclude
                     outhistogram = OutMdpts;
run;

Output 4.18.3 differs from Output 4.18.2 in two ways:

Output 4.18.3 Histogram with MIDPOINTS= and RTINCLUDE Options
Histogram with MIDPOINTS= and RTINCLUDE Options

The OUTHISTOGRAM= option produces an output data set named OutMdpts, displayed in Output 4.18.4. This data set provides information about the bins of the histogram. For more information, see the section OUTHISTOGRAM= Output Data Set.

Output 4.18.4 The OUTHISTOGRAM= Data Set OutMdpts
Enhancing a Histogram

Obs _VAR_ _MIDPT_ _OBSPCT_ _COUNT_
1 Thick 3.4375 9 9
2 Thick 3.4625 21 21
3 Thick 3.4875 26 26
4 Thick 3.5125 28 28
5 Thick 3.5375 11 11
6 Thick 3.5625 5 5

A sample program for this example, uniex08.sas, is available in the SAS Sample Library for Base SAS software.

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