Hello List! I stumbled across an efficiency problem - calculation that would be probably done very fast as a matrix operation I must perform as a for-loop. My intention was to do a conditional operation in matrix depending on the information in first column (summing as many data points from vector my_data as the number specified in the first column of the matrix) but the result is that the function takes the condition only from the first row of column for calculations in every row. Is it possible to solve this problem as a matrix calculation or I have to iterate over each row? (which I suppose is much slower)
#problem looks like: my_mat <- matrix(1:50,ncol=2) my_mat <- cbind(my_mat,0) #here I have a matrix with empty third column where I want to store my results my_data <- rnorm(25) #this is a dataset I want to use for filling the third column #and I did my_mat[,3] <- sum(my_data[1:my_mat[,1]]) + my_mat[,2] #which didn't work as I expected Hope I will get some suggestions, Lukasz ______________________________________________ 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.
