Getting Started: CANDISC Procedure

The data in this example are measurements of 159 fish caught in Finland’s lake Laengelmavesi; this data set is available from the Puranen. For each of the For each of the seven species (bream, roach, whitefish, parkki, perch, pike, and smelt) the weight, length, height, and width of each fish are tallied. Three different length measurements are recorded: from the nose of the fish to the beginning of its tail, from the nose to the notch of its tail, and from the nose to the end of its tail. The height and width are recorded as percentages of the third length variable. The following statements create the SAS data set:

   title 'Fish Measurement Data';
   
   proc format;
      value specfmt
         1='Bream'
         2='Roach'
         3='Whitefish'
         4='Parkki'
         5='Perch'
         6='Pike'
         7='Smelt';
   run;
   
   data fish (drop=HtPct WidthPct);
      input Species Weight Length1 Length2 Length3 HtPct
            WidthPct @@;
      Height=HtPct*Length3/100;
      Width=WidthPct*Length3/100;
      format Species specfmt.;
      symbol = put(Species, specfmt2.);
      datalines;
   1  242.0 23.2 25.4 30.0 38.4 13.4 1  290.0 24.0 26.3 31.2 40.0 13.8
   
   ... more lines ...   

   7   19.7 13.2 14.3 15.2 18.9 13.6 7   19.9 13.8 15.0 16.2 18.1 11.6
   ;

The next steps use PROC CANDISC to find the three canonical variables that best separate the species of fish in the fish data and create the output data set outcan. With the NCAN=3 option, only the first three canonical variables are displayed. The ODS EXCLUDE statement is specified to exclude the canonical structure tables and most of the canonical coefficient tables in order to obtain a more compact set of results. The TEMPLATE and SGRENDER procedures within ODS Graphics are invoked to create a plot of the first two canonical variables. The following statements produce Figure 27.1 through Figure 27.6:

   proc candisc data=fish ncan=3 out=outcan;
      ods exclude tstruc bstruc pstruc tcoef pcoef;
      class Species;
      var Weight Length1 Length2 Length3 Height Width;
   run;
   
   proc template;
      define statgraph scatter;
         begingraph;
            entrytitle 'Fish Measurement Data';
            layout overlayequated / equatetype=fit
               xaxisopts=(label='Canonical Variable 1')
               yaxisopts=(label='Canonical Variable 2');
               scatterplot x=Can1 y=Can2 / group=species name='fish';
               layout gridded / autoalign=(topright);
                  discretelegend 'fish' / border=false opaque=false;
                  endlayout;
            endlayout;
         endgraph;
      end;
   run;
   
   proc sgrender data=outcan template=scatter;
   run;

PROC CANDISC begins by displaying summary information about the variables in the analysis. This information includes the number of observations, the number of quantitative variables in the analysis (specified with the VAR statement), and the number of classes in the classification variable (specified with the CLASS statement). The frequency of each class is also displayed.