survival::survfit,plot.survfit

plot(survfit(fit)) should plot the survival-function for x=0 or 
equivalently beta'=0. This curve is independent of any covariates.
This is not correct.  It plots the curve for a hypothetical subject with x= 
mean of each covariate.  
  This is NOT the "average survival" of the data set.  Imagine a cohort made up 
of 60 year old men and their 10 year old grandsons: the expected survival of 
this cohort does not look that for a 35 year old male.

  	Terry T
Thanks very much, Bernhard and Terry.
It clarify my confusion and really helps a lot.

Regards
Jeff Xu

plot(survfit(fit)) should plot the survival-function for x=0 or 
equivalently beta'=0. This curve is independent of any covariates.
  This is not correct.  It plots the curve for a hypothetical subject with
x= 
mean of each covariate.  
  This is NOT the "average survival" of the data set.  Imagine a cohort
made up 
of 60 year old men and their 10 year old grandsons: the expected survival
of 
this cohort does not look that for a 35 year old male.

  	Terry T

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plot(survfit(fit)) should plot the survival-function for x=0 or
equivalently beta'=0. This curve is independent of any covariates.
  This is not correct.  It plots the curve for a hypothetical 
subject with x=
mean of each covariate.
Does this mean, the curve corresponds to the one you would get based 
on the base line hazard?

Heinz
  This is NOT the "average survival" of the data set.  Imagine a 
cohort made up
of 60 year old men and their 10 year old grandsons: the expected survival of
this cohort does not look that for a 35 year old male.

        Terry T

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.