The SIMILARITY Procedure

This simple example illustrates how to use similarity analysis to compare two time sequences. The following statements create an example data set that contains two time sequences of differing lengths:

data test;
input i y x;
datalines;
1   2  3
2   4  5
3   6  3
4   7  3
5   3  3
6   8  6
7   9  3
8   3  8
9  10  .
10 11  .
;
run;

The following statements perform similarity analysis on the example data set:

proc similarity data=test out=_null_
   print=all plot=all;
   input x;
   target y / measure=absdev;
run;

The DATA=TEST option specifies that the input data set WORK.TEST is to be used in the analysis. The OUT=_NULL_ option specifies that no output time series data set is to be created. The PRINT=ALL and PLOTS=ALL options specify that all ODS tables and graphs are to be produced. The INPUT statement specifies that the input variable is X. The TARGET statement specifies that the target variable is Y and that the similarity measure is computed using absolute deviation (MEASURE=ABSDEV).

The following statements repeat the preceding similarity analysis on the example data set with warping limits:

proc similarity data=test out=_null_
   print=all plot=all;
   input x;
   target y / measure=absdev
              compress=(localabs=2)
              expand=(localabs=2);
run;

The COMPRESS=(LOCALABS=2) option limits local absolute compression to 2. The EXPAND=(LOCALABS=2) option limits local absolute expansion to 2.

The following statements repeat the preceding similarity analysis on the example data set but store the results in output data sets:

proc similarity data=test out=series
   outsequence=sequences outpath=path outsum=summary;
   input x;
   target y / measure=absdev
              compress=(localabs=2)
              expand=(localabs=2);
run;

The OUT=SERIES, OUTSEQUENCE=SEQUENCES, OUTPATH=PATH, and OUTSUM=SUMMARY options specify that the output time series, time sequences, path analysis, and summary data sets be created, respectively.