Hello all,

I have a dataset that I was hoping to run cox PH regressions on using Cyclops, but in the process of comparing results against the same regression with coxph I found that I was getting different results. The coxph results are agreeing with previous SAS modeling I’m validating against. It seems to be coming down to the two functions returning different values for the log-likelihood. I’m getting values in the scale of -67000 with coxph and -91000 with Cyclops.

I’ve been running the two with every output and modeling option I can find, but I can’t figure out where the two are differing. Its not an issue with how they are handling ties or normalization. They both report the same number of rows and events. I’m inputting the same data.frame and formula object to both functions. To my understanding the log-likelihood should have a similar computation no matter what library I’m using, its just a difference in how the iteration is performed. It seems way too far off to be some kind of simplification or rounding that Cyclops is doing.

I wanted to run my situation by the forum to see if anyone more experienced has a suggestion of where to look.

Thank you for your time.