Hi, Philip,
counter-questions:
1. Which/where is the grouping variable for the test of differences in
survival?
2. Assume the grouping variable is Gend in B27.vec. Then, why aren't you
using
survdiff( Surv( AgeOn, UV) ~ Gend, rho = 0, data = B27.vec)
?
Hth -- Gerrit
On Thu, 26 Jan 2012, Philip Robinson wrote:
Hi,
I have a data frame:
class(B27.vec)
[1] "data.frame"
head(B27.vec)
AGE Gend B27 AgeOn DD uveitis psoriasis IBD CD UC InI BASDAI BASFI Smok UV
1 57 1 1 19 38 2 1 1 1 1 1 5.40 8.08 NA 1
2 35 1 1 33 2 2 1 1 1 1 1 1.69 2.28 NA 1
3 49 2 1 40 9 1 1 1 1 1 1 8.30 9.40 NA 0
4 32 1 1 21 11 1 1 1 1 1 1 5.10 9.10 NA 0
5 31 1 1 24 7 1 1 1 1 1 1 6.63 6.52 NA 0
6 27 1 1 23 4 1 2 1 1 1 1 7.19 6.51 NA 0
I am trying to perform survival analysis but continually get errors
when extracting from this data.frame:
attempt 1:
X <- Surv(B27.vec$AgeOn,B27.vec$UV)
survdiff(X,rho=0,data=uvf)
Error in x$terms : $ operator is invalid for atomic vectors
attempt 2:
X <- Surv(B27.vec[,4],B27.vec[,15])
survdiff(X,rho=0,data=uvf)
Error in x$terms : $ operator is invalid for atomic vector
attempt 3:
AO <- B27.vec[["AgeOn", exact = TRUE]]
UV <- B27.vec[["UV",exact=TRUE]]
X <- Surv(AO,UV)
survdiff(X,rho=0,data=uvf)
Error in x$terms : $ operator is invalid for atomic vectors
I have read ?data.frame & extract.data.frame but I cannot understand
how I might structure this differently so it extracts the required
columns from this dataframe. For the second 2 attempts I am not using
the $ term. Sorry if this seems basic but cannot understand why
attempt 1 or 2 doesn't work.
thanks
Philip
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and provide commented, minimal, self-contained, reproducible code.