Re: [R] Is there an equivalent to predict(..., type=linear) of a Proportional hazard model for a Cox model instead?

2010-11-26 Thread Terry Therneau
1. survreg() does NOT fit a proportional hazards model, a mistake repeated multiple times in your post 2. The coxph function operates on the risk scale: large values of Xbeta = large death rates = bad The survreg operates on the time scale: large values of xbeta = longer liftetime = good. 3.

Re: [R] Is there an equivalent to predict(..., type=linear) of a Proportional hazard model for a Cox model instead?

2010-11-26 Thread Ben Rhelp
Hi Terry, David, and Thomas, Thank you for all your emails and the time you to took to clarify my misunderstanding on survival analysis. I will need a bit of time to digest all this information and to do some more reading. Best regards, Ben From: Terry Therneau 1. survreg() does NOT

Re: [R] Is there an equivalent to predict(..., type=linear) of a Proportional hazard model for a Cox model instead?

2010-11-25 Thread Ben Rhelp
I manage to achieve similar results with a Cox model as follows but I don't really understand why we have to take the inverse of the linear prediction with the Cox model and why we do not need to divide by the number of days in the year anymore? Am I getting a similar result out of pure luck?

Re: [R] Is there an equivalent to predict(..., type=linear) of a Proportional hazard model for a Cox model instead?

2010-11-25 Thread David Winsemius
On Nov 25, 2010, at 7:27 AM, Ben Rhelp wrote: I manage to achieve similar results with a Cox model as follows but I don't really understand why we have to take the inverse of the linear prediction with the Cox model Different parameterization. You can find expanded answer(s) in the

Re: [R] Is there an equivalent to predict(..., type=linear) of a Proportional hazard model for a Cox model instead?

2010-11-25 Thread Ben Rhelp
Hi David, Thank you for your reply. See below for more information. From: David Winsemius On Nov 25, 2010, at 7:27 AM, Ben Rhelp wrote: I manage to achieve similar results with a Cox model as follows but I don't really understand why we have to take the inverse of the linear

Re: [R] Is there an equivalent to predict(..., type=linear) of a Proportional hazard model for a Cox model instead?

2010-11-25 Thread David Winsemius
On Nov 25, 2010, at 10:08 AM, Ben Rhelp wrote: Hi David, Thank you for your reply. See below for more information. From: David Winsemius On Nov 25, 2010, at 7:27 AM, Ben Rhelp wrote: I manage to achieve similar results with a Cox model as follows but I don't really understand why

Re: [R] Is there an equivalent to predict(..., type=linear) of a Proportional hazard model for a Cox model instead?

2010-11-25 Thread David Winsemius
I hit the send button on my second reply before I intended to. Since then I have noticed that the question I thought you were asking is not at all a good match to the Subject line of your message. There is a type =lp in predict.coxph and that is the linear predictor, although it is not a

[R] Is there an equivalent to predict(..., type=linear) of a Proportional hazard model for a Cox model instead?

2010-11-24 Thread Ben Rhelp
Hi all, Is there an equivalent to predict(...,type=linear) of a Proportional hazard model for a Cox model instead? For example, the Figure 13.12 in MASS (p384) is produced by: (aids.ps - survreg(Surv(survtime + 0.9, status) ~ state + T.categ + pspline(age, df=6), data = Aidsp)) zz -