Hi, I have a data frame with 15 different years and each year has a different sample size. I'm having trouble writing a for loop to have a t-test done for each year for two of the columns. Thus far I have been able to loop over the years but the output is the same t-test 15 times. I'm new to writing loops and functions, and am trying to figure out a way to use them together (if there are any general rules to follow, I would be great-full to know)
for(year in 1998:2012){ b <-t.test(tr$adj_ind_pop_dif, tr$ind_nei_dif, paired=TRUE) print(b) } the other way I did it was to take subsets of the dataframe and then do a separate t-test for each ab<-subset(tr, BroedJaar =="1999") t.test(ab$ind_nei_dif, ab$adj_ind_pop_dif, paired=TRUE) Best, Monaly. [[alternative HTML version deleted]] ______________________________________________ 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.