[R] Survdiff for multiple comparisons

Danielle Zoellner
Thu, 21 Jul 2011 14:57:34 -0000

Hello all-

I am doing a survival analysis for two species of invasive plants I
outplanted to edges and interiors of island and mainland sites in a local
reservoir.  I am using the KM estimate and had no problem doing survdiff for
my data using the following code:

S4<-Surv(outplant$SurvTime, outplant$StatusD6)
diff4=survdiff(S4 ~ outplant$Species+outplant$SiteType+outplant$EdgInt)
diff4

Species = ALBIJU or LONIJA
SiteType = Island or Mainland
EdgInt = Edge or Interior

The overall test for difference among the 8 curves is highly significant
(p<0.001), but what I would like to know is how I would go about testing for
pairwise differences among the eight curves, as what is most informative
would be pinpointing exactly which curves are significantly different from
each other for each species.  I have not been able to find any code or
function out there that will give me this test with adjusted p-values.  I
was thinking about using subset, but this will not adjust the p-values for
multiple tests.

Thank you for your time - Danielle

--
Danielle C. Zoellner-Kelly
PhD candidate - DeWalt Lab
Department of Biological Sciences
Clemson University
132 Long Hall
Clemson, SC   29634
Lab:  (864) 656-2639
Cell:  (864) 376-9583

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