* LIFETST2.SAS
* xref:  Cox & Oakes table 1.1
* input:   6-MP   DATA A
* output:
* does: - demonstrate proc lifetest - KM estimates and plots
        - 2 samples
***************************************************;
filename INF '6-MP.DAT';
options linesize=176;
***************************************************;
data A;
  infile INF;
  input time delta group;
  label
    time  = 'Follow-up time (wks)         ..'
    delta = 'Event: 0=censored 1=observed ..'
    group = 'Group: 0=control  1=drug     ..'
  ;
  run;
***************************************************;
proc lifetest data = A  method=KM  outs=B alpha=0.05 plots=(s, ls, lls);
  strata group;               * -->       try also: by     group;
  time time * delta(0);
  title2 'proc lifetest output';
  run;
***************************************************;
data C;
  set B;
  if not _censor_;
  * compute intervals on the log-scale;
  sdf_lcl = survival * exp(sdf_lcl/survival-1);
  sdf_ucl = survival * exp(sdf_ucl/survival-1);
  if (sdf_ucl > 1) then  sdf_ucl = 1;
  drop _censor_;
  run;
***************************************************;
proc print data=C;
  title2 'proc print    output';
  run;
***************************************************;
proc plot data=C;
  plot (sdf_lcl survival sdf_ucl)  * time   = group
     / overlay  vaxis = 0 to 1 by 0.1;
  title2 'proc plot     output';
  run;