Speed up the loop operation in R

Question

I have a big performance problem in R. I wrote a function that iterates over a data.frame object. It simply adds a new column to a data.frame and a

Answer 1

This could be made much faster by skipping the loops by using indexes or nested ifelse() statements.

idx <- 1:nrow(temp)
temp[,10] <- idx
idx1 <- c(FALSE, (temp[-nrow(temp),6] == temp[-1,6]) & (temp[-nrow(temp),3] == temp[-1,3]))
temp[idx1,10] <- temp[idx1,9] + temp[which(idx1)-1,10] 
temp[!idx1,10] <- temp[!idx1,9]    
temp[1,10] <- temp[1,9]
names(temp)[names(temp) == "V10"] <- "Kumm."