[R] understanding the output from survival analysis

[Chris Andrews]

Ullrika Sahlin <ullrika.sahlin <at> ekol.lu.se> writes:

> 
> Why do I get different sign of the coefficients of covariates when I run the
> semi-parametric proportional hazard model (coxph) compared to the parametric
> proportional hazard model (survreg)?
> 
> Anyone with experience in extracting information from survreg to make
> predictions are free to contact me.
> 
> Cheers,
> 
> Ullrika 
> 

coxph fits a proportional hazards model.
survreg fits an accelerated failure time model.

These are parametrized differently.  In the first, a higher linear predictor
means greater hazard (i.e., shorter lifetime).  In the second, a higher linear
predictor means greater expected (log) lifetime.

Consult an introductory survival text such as Klein and Moeschberger for more on
these types of model.  The Design library may help you with predictions.

Chris