title: How to predict probability in logistic regression in SAS?
body: <p>I am very new to SAS and trying to predict probabilities using logistic regression in SAS. I got the code below from SAS Support web site: </p>
  
  <pre><code>  data vaso;
    length Response $12;
    input Volume Rate Response @@;
    LogVolume=log(Volume);
    LogRate=log(Rate);
    datalines;
  3.70  0.825  constrict       3.50  1.09   constrict
  1.25  2.50   constrict       0.75  1.50   constrict
  0.80  3.20   constrict       0.70  3.50   constrict
  0.60  0.75   no_constrict    1.10  1.70   no_constrict
  0.90  0.75   no_constrict    0.90  0.45   no_constrict
  0.80  0.57   no_constrict    0.55  2.75   no_constrict
  0.60  3.00   no_constrict    1.40  2.33   constrict
  0.75  3.75   constrict       2.30  1.64   constrict
  3.20  1.60   constrict       0.85  1.415  constrict
  1.70  1.06   no_constrict    1.80  1.80   constrict
  0.40  2.00   no_constrict    0.95  1.36   no_constrict
  1.35  1.35   no_constrict    1.50  1.36   no_constrict
  1.60  1.78   constrict       0.60  1.50   no_constrict
  1.80  1.50   constrict       0.95  1.90   no_constrict
  1.90  0.95   constrict       1.60  0.40   no_constrict
  2.70  0.75   constrict       2.35  0.03   no_constrict
  1.10  1.83   no_constrict    1.10  2.20   constrict
  1.20  2.00   constrict       0.80  3.33   constrict
  0.95  1.90   no_constrict    0.75  1.90   no_constrict
  1.30  1.625  constrict
  ;
  ods graphics on;
  
  proc logistic data=vaso PLOTS = (ROC EFFECT);
    model Response(event='constrict')=LogRate LogVolume 
    /ctable pprob=0.5 selection=forward rsquare link=logit expb ;
  run;
  ods graphics off; 
  </code></pre>
  
  <p>I am wondering how I could predict the probability when I have <code>logVolume= 1.5</code> and <code>logRate=1.3</code>. Also, can you please explain what <code>length Response $12</code> above means?</p>