options nodate pagesize=54 linesize=80;

/* Read in the input file   */

data ex0803;
* infile '../../../data/biostat/ex0803.dat';
infile 'C:\biostat\data\ex0803.dat';
input subj rnachng auc0_6;
run;

/* Fit the nonlinear regression model (S-shaped)  */
/* For possible starting values, note:
   When AUC=0, RNACHNG=0 (if b1 not 0)
   When AUC gets huge, RNACHNG=b0 (Points flatten out around b0=4)
   When AUC=b1, RNACHNG=b0/2, so set b1 at 18000 (about where the points are 2)
   b2 is related to steepness, try b2=10 (this is steep curve)a  */

proc nlin;
parms b0=4 b1=18000 b2=10;
model rnachng = (b0*(auc0_6**b2))/((auc0_6**b2)+(b1**b2));
run;




quit;