Retain or Lag?

[ChuksManuel]

Hello guys,

I have 5 models 0, 1,2,3,4. My variables are  tool1, tool2, tool3, tool5, tool6, tool11, tool12 and AUC

data one;
input modelstep TOOL1 TOOL2 TOOL3 TOOL5 TOOL6 TOOL11 TOOL12 AUC 
datalines;
0 -0.097544 0.38682 -0.057215 0.19231 0.013377 -0.35196 0.58613 0.69676 
1 -0.097379 0.3858 -0.057377 0.19214 0.013363 -0.35187 0.58526 0.69668 
2 -0.096809 0.38621 -0.057295 0.19177 0.013297 -0.35061 0.58444 0.69618 
3 -0.09729 0.38838 -0.057003 0.19405 0.013242 -0.34783 0.57736 0.69666 
4 -0.096492 0.3881 -0.054853 0.19513 0.013091 -0.33446 0.57587 0.6963 
; run;

Data two;
set one;
retain difference_from_model0;
if first.AUC then difference_from_model0=0;
if last.id then output;
proc print; run;

i basically want to write a code to find the difference in AUC between model 0 and the other models (model 1 to model 4). Simply put , model 0- model1 will be first observation. model 0 - model 2 will be second observation. model 0 - model 3 will be third observation etc. 

I want my final output to be something like this

modelstep TOOL1 TOOL2 TOOL3 TOOL5 TOOL6 TOOL11 TOOL12 AUC Difference_from_model0

1 -0.097379 0.3858 -0.057377 0.19214 0.013363 -0.35187 0.58526 0.69668 xxxx
2 -0.096809 0.38621 -0.057295 0.19177 0.013297 -0.35061 0.58444 0.69618 yyyy
3 -0.09729 0.38838 -0.057003 0.19405 0.013242 -0.34783 0.57736 0.69666 zzzz
4 -0.096492 0.3881 -0.054853 0.19513 0.013091 -0.33446 0.57587 0.6963 cccc

I tried to use the retain function but have not been successful. My code is attached. Any help will be appreciated.

Thanks

[ChuksManuel]

Here's a modification of my code. It's still not giving me any output that's meaningful. 

data two;
 set one;
  by outcome;
 retain difference_AUC_model0;
 if first.modelstep then difference_AUC_model0 = AUC;
 else difference_AUC_model0 = difference_AUC_model0 - AUC;
 run;  
proc print; run;

[Tom · Accepted solution]

It does not look like you have any BY groups in that data.  It is all one group with different values of MODELSTEP.

data want ;
  set one;
  retain AUC0;
  if modelstep=0 then AUC0 = AUC ;
  diff = AUC - AUC0;
run;

If you have multiple models (each of which can have one or more steps) then you could use BY processing.

data want ;
  set one;
  by model;
  retain AUC0;
  if first.model then AUC0=.;
  if modelstep=0 then AUC0 = AUC ;
  diff = AUC - AUC0;
run;

[ChuksManuel]

Thank you Tom.

Thank was indeed helpful