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 ______________________________________________ R-help@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.