Resending after fixing a mistake in the earlier email ... sorry for the confusion.
****** Dear R-Users, I need to lookup values from a 2-d table using the row names and column names as indices. I was wondering if there's a way to do this without an explicit loop. Example: #x is the 2-d table that holds the values x <- matrix(rnorm(26*12),nrow=26) rownames(x) <- letters colnames(x) <- month.name #y is a data frame that has the "keys" I want to use as indices into x y <- data.frame(ltrs=sample(letters,5),mnths=sample(month.name,5),values=0) #I want to fill in the "values" column using the "ltrs" and "mnths" columns as keys to look up # the associated value from x #One way to do this is with a FOR loop for (i in 1:nrow(y)) {y$values[i] <- x[as.character(y$ltrs[i]),as.character( y$mnths[i])]} My question: Is there a more efficient way (e.g., one without using an explicit loop) to do this? Thanks in advance! -Rama Ramakrishnan [[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.