cheers for the reply Rick. The format applies to the group variable and it has 8 categories. 4 of the categories (or lines in the plot) correspond to the first series and were okay, the other 4 caused the problem. I should say: I am plotting hazard ratios; in the first series they were between maybe 0 and 2, but in the second series some might have exceeded 1000 owing to a miscalculation (when i used the hazardratio statement in phreg, instead of calculating by hand, the problem was resolved, sgplot ran because the HRs were now sensible values) i think my use of " ANTIALIASing" was superfluous here and a hangover from other code that i'd copied across. Unfortunately i'm unable to test your hypothesis because the code was further developed and no longer producing the extreme values edit: the reason i suspect the extreme values are to blame is because sgplot ran fine, even with antialiasing, until i modified the equations for HRs which i suspect blew out the estimates, and then sgplot hung
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