Modern R Programming Cookbook

How to do it…

Write a function using a for loop to execute the targeted operation. Also, write another function without using a loop. Let's take a look at the following steps and see how we can do the preceding two tasks:

1. Execute the following code snippet that depicts a function using a loop:

        loopOperation <- function(mat){          out<-matrix(NA, nrow = ncol(mat), ncol = ncol(mat))          for(i in 1:ncol(mat)){            for(j in 1:ncol(mat)){              colI <- mat[,i]              colJ <- mat[,j]              out[i,j] <- t(colI) %*% colJ            }          }         return(out)        }

2. Execute another function without using the loop, but use only the matrix operation as shown in the following code snippet:

        vectorizedOp <- function(mat){          return(t(mat) %*% mat)        } library(microbenchmark) # To compare performance of the functions ...