Eleni Rapsomaniki wrote:
Dear R-users,
One can use the rcorr.cens function in Design to compute the C index when only the stop time is indicated (I think implicitely start=0 in that case). When the start and stop times are used in a Surv object, e.g.
library(Design)
S=with(heart, Surv(start,stop,event))
the object returned is no longer a single number vector, so none of the
following ways to compare a model fit to S makes sense:
rcorr.cens(-cph(S~ age+transplant+surgery, heart)$linear.predictors,
with(heart, Surv(start,stop,event)))
# C Index Dxy S.D. n missing
# 4.95e-01 -9.66e-03 7.15e-02 1.72e+02 0.00e+00
#this seems bad because it compares the fit to a different Surv than the one used to fit it (S, above)
rcorr.cens(-cph(S~ age+transplant+surgery, heart)$linear.predictors,
with(heart, Surv(stop-start,event)))
# C Index Dxy S.D. n missing
# 6.02e-01 2.03e-01 7.54e-02 1.72e+02 0.00e+00
Is there some way I can compute the correlation for this type of survival time
specification in R? If not, does anybody have some tips on how to go about
computing it myself?
Many Thanks
Eleni Rapsomaniki
Research Associate
Strangeways Research Laboratory
Department of Public Health and Primary Care
University of Cambridge
rcorr.cens is not meant for that.
Frank
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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