# Utility function to generate tail-oriented window Utility function to generate tail-oriented windows inputs given the approximate number of subpopulations desired. ```r gen.tailwin(covariate, nsub, dir="LE") ``` ## Arguments - `covariate`: covariate values - `nsub`: number of tail-oriented subpopulations to be generated - `dir`: "LE" (default) or "GE" - subpopulations with covariate values less than or equal/greater than or equal to the generated values ## Returns It returns a list with fields: $v - vector of covariate values to be used in the constructor stepp.win. $np - vector of subpopulation size associate with each tail-oriented window defined by $v. ## Details Use this together with the constructor, stepp.win, to generate tail-oriented windows. ## Author(s) Wai-ki Yip ## See Also `stwin`, `stepp.win` ## Examples ```r data(bigKM) rxgroup <- bigKM$trt time <- bigKM$time evt <- bigKM$event cov <- bigKM$ki67 # analyze using Kaplan-Meier method with tail-oriented window # nsubpop_tmp <- 10 win_tmp <- gen.tailwin(cov, nsub = nsubpop_tmp, dir = "LE") nsubpop <- length(win_tmp$v) # create a tail-oriented window swin <- new("stwin", type = "tail-oriented", r1 = win_tmp$v, r2 = rep(min(cov), nsubpop)) subp <- new("stsubpop") # create subpopulation object subp <- generate(subp, win = swin, covariate = cov) # generate the subpopulations summary(subp) # summary of the subpopulations # create a stepp model using Kaplan Meier Method to analyze the data # smodel <- new("stmodelKM", coltrt=rxgroup, trts=c(1,2), survTime=time, censor=evt, timePoint=4) statKM <- new("steppes") # create a test object based on subpopulation and window statKM <- estimate(statKM, subp, smodel) # estimate the subpopulation results # Warning: IT IS RECOMMEND TO USE AT LEAST 2500 PERMUTATIONS TO PROVIDE STABLE RESULTS. statKM <- test(statKM, nperm = 10) # permutation test with 10 iterations print(statKM) # print the estimates and test statistics plot(statKM, ncex=0.65, legendy=30, pline=-15.5, color=c("blue","gold"), pointwise=FALSE, xlabel="Median Ki-67 LI in Subpopulation (% immunoreactivity)", ylabel="4-year Disease Free Survival", tlegend=c("Letrozole", "Tamoxifen"), nlas=3) ```

gen.tailwin function