/* firefly1.sas */
options ls=72 ps=60;
data firefly0;
   infile 'firefly.dat';
   input date condition $ time temp light;
   code = condition;
   if condition = 'cloudy' then code = 'y';
proc plot data=firefly0;
   plot time*light = code;
   plot time*temp = code;
   plot light*temp = code;
title 'plots with overcast included';
/* remove observations for overcast days */
data firefly;
   set firefly0;
   if condition = 'overcast' then delete;
proc plot data=firefly;
   plot time*light = code;
   plot time*temp = code;
   plot light*temp = code;
title 'plots with overcast excluded';   
/* fit models */
/* regression of time on temp and light (full model) */
proc glm data=firefly;
   model time = temp light / ss1 ss2 clparm;
      output out=new1 predicted=yhat residual=resid
          lcl=clpl ucl=clpu lclm=clml uclm=clmu;
title 'regression of time on temp and light (full model)';
proc print data=new1;
   var time temp light clml clmu clpl clpu yhat resid;
proc plot data=new1;
   plot resid*yhat / vref=0;
   plot resid*temp / vref=0;
   plot resid*light / vref=0;
   plot resid*date / vref=0;   
title 'residual plots: full model';
/* regression of time on light and temp (full model) */
proc glm data=firefly;
   model time = light temp / ss1 ss2 clparm;
title 'regression of time on temp and light (full model)';
/* regression of time on temp (reduced model) */
proc glm data=firefly;
   model time = temp / ss1 ss2 clparm;
      output out=new2 predicted=yhat residual=resid
          lcl=clpl ucl=clpu lclm=clml uclm=clmu;
title 'regression of time on temp (reduced model)';
proc print data=new2;
   var time temp clml clmu clpl clpu yhat resid;
proc plot data=new2;
   plot resid*yhat / vref=0;
   plot resid*temp / vref=0;
   plot resid*light / vref=0;
   plot resid*date / vref=0;   
title 'residual plots: reduced model (temp only)';
/* regression of time on light (reduced model) */
proc glm data=firefly;
   model time = light / ss1 ss2 clparm;
      output out=new3 predicted=yhat residual=resid
          lcl=clpl ucl=clpu lclm=clml uclm=clmu;
title 'regression of time on light (reduced model)';
proc print data=new3;
   var time temp clml clmu clpl clpu yhat resid;
proc plot data=new3;
   plot resid*yhat / vref=0;
   plot resid*temp / vref=0;
   plot resid*light / vref=0;
   plot resid*date / vref=0;   
title 'residual plots: reduced model (light only)';
/* use proc reg to get sequential regression coefficients */
proc reg data=firefly;
   model time = temp light / seqb ss1 ss2;
   model time = light temp / seqb ss1 ss2;
title 'regressions with sequential coefficients';   
/* get adjusted explanatory variables */
/* regression of light on temp for adjustment of light */
proc glm data=firefly;
   model light = temp / ss1 ss2;
      output out=newlight r=adjlight;
title 'regression of light on temp for adjustment of light';
proc print data=newlight;
   var time temp adjlight;
proc plot data=newlight;
   plot adjlight*temp;
   plot time*adjlight;
proc glm data=newlight;
   model time = temp adjlight /ss1 ss2;
title 'regression of time on temp and adjlight';       
/* regression of temp on light for adjustment of temp */
proc glm data=firefly;
   model temp = light / ss1 ss2;
      output out=newtemp r=adjtemp;
title 'regression of temp on light for adjustment of temp';
proc print data=newtemp;
   var time light adjtemp;
proc plot data=newtemp;
   plot adjtemp*light;
   plot time*adjtemp;
proc glm data=newtemp;
   model time = light adjtemp /ss1 ss2;
title 'regression of time on light and adjtemp';    
run;