Hi R user, I'm new to R so my problem is probably pretty simple but I'm stuck:
my data is consist of 2 variables: co2, temp and one treatment (l_group). The sample size is different among the treatments. so that, I wanted to make equal sample size among three groups (A,B and C) of the treatment. For this one, I used subsamples technique. Using subsample, each time the data are different among the three groups of the treatment. so that I want to run regression (co2~temp) for a 100 subsamples for each group of treatment (100 times subsample). it means that I will have 100 regression equations. Later, I want to compare the slope of the regression among the three groups. is there simple way to make a loop so that I can compare it? Thanks in advance! Angela ================ Here is the example: dat<-structure(list(co2 = c(0.15, 0.148, 0.125, 0.145, 0.138, 0.23, 0.26, 0.35, 0.41, 0.45, 0.39, 0.42, 0.4, 0.43, 0.26, 0.3, 0.34, 0.141, 0.145, 0.153, 0.151, 0.128, 0.23, 0.26), temp = c(0.0119, 0.0122, 0.0089, 0.0115, 0.0101, 0.055, 0.097, 0.22, 0.339, 0.397, 0.257, 0.434, 0.318, 0.395, 0.087, 0.13, 0.154, 0.0107, 0.0112, 0.0119, 0.012, 0.0092, 0.055, 0.089), L_group = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), .Label = c("A", "B", "C"), class = "factor")), .Names = c("co2", "temp", "L_group"), class = "data.frame", row.names = c(NA, -24L )) head(dat) library(sampling) # strata.sampling ----- strata.sampling <- function(data, group,size, method = NULL) { require(sampling) if (is.null(method)) method <- "srswor" temp <- data[order(data[[group]]), ] ifelse(length(size)> 1, size <- size, ifelse(size < 1, size <- round(table(temp[group]) * size), size <- rep(size, times=length(table(temp[group]))))) strat = strata(temp, stratanames = names(temp[group]), size = size, method = method) getdata(temp, strat) } #-------------------------------------------------- sub_dat <- strata.sampling(dat, 'L_group', 4)# Lmodel_subdata1<-lm(co2~temp, data=subdat) Lmodel_subdata1#coef sub_dat2 <- strata.sampling(dat, 'L_group', 4)# Lmodel_subdata2<-lm(co2~temp, data=subdat2) Lmodel_subdata2#coef and so on.....[for 100 times) Table<-rbind(Lmodel_subdata1$coef, Lmodel_subdata1$coef, ....) ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.