Consider the data.frame: df <- data.frame(A = c(1,4,2,6,7,3,6), B= c(3,7,2,7,3,5,4), C = c(2,7,5,2,7,4,5), index = c("A","B","A","C","B","B","C"))
I want to select the column specified in 'index' for every row of 'df', to get goal <- c(1, 7, 2, 2, 3, 5, 5) This sounds a lot like the indexing-by-a-matrix you can do with arrays; df[cbind(1:nrow(df), df$index)] but this returns me values that are all characters where I want numbers. (it seems that indexing by an array isn't well supported for data.frames.) What is a better way to perform this selection operation? Peter [[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.