how do I search for columns with same name, add the column values and replace these columns with same name by their sum? Using R

Question

I have a data frame where some consecutive columns have the same name. I need to search for these, add their values in for each row, drop one column and replace the other wi

Answer 1

One way is to identify duplcates using (surprise) the duplicated function, and then loop through them to calculate the sums. Here is an example:

dat.dup <- data.frame(x=1:10, x=1:10, x=1:10, y=1:10, y=1:10, z=1:10, check.names=FALSE)
dups <- unique(names(dat.dup)[duplicated(names(dat.dup))])
for (i in dups) {
dat.dup[[i]] <- rowSums(dat.dup[names(dat.dup) == i])
}
dat <- dat.dup[!duplicated(names(dat.dup))]