onlineclass/ProgrammingAssignment2: Repository for Programming Assignment 2 for R Programming on Coursera · GitHub

This repository contains the solution to the second programming assignment of the R Programming course: Caching the Inverse of a Matrix. The repository has been created by clonning @rdpeng/ProgrammingAssignment2. The original README.md file has been renamed to original.repo.README.md Following is a brief description of each file:

• README.md - this file
• original.repo.README.md - the assignment specification (original README.md)
• cachematrix.R - R script containing the assignment solution
• performanceTest.R - R script for performance testing/comparison

The two functions implemented in the cachematrix.R script (makeCacheMatrix and cacheSolve) have been briefly described via the comments in R script (as recommended in the assignment specification). To check the cachematrix.R script, simply open it in the web browser or download it in a folder on your computer and open it in R Studio. After downloading the R scripts in the R working directory, the following code sequence can be used to test the two functions implemented in cachematrix.R. The statements will perform the following tasks:

1. create list object cache_m with makeCacheMatrix() function
2. create a square (100x100) matrix m with random data
3. set the data of cache_m by calling cache_m$set(m)
4. compute the inverse of m using direct_inverse <- solve(m)
5. compute the inverse of m using cached_inverse <- cacheSolve(cache_m)
6. check the direct_inverse and cached_inverse are equal

source("cachematrix.R")
cache_m <- makeCacheMatrix()
m <- matrix(runif(10000, -3, 3), nrow = 100, ncol = 100)
cache_m$set(m)
direct_inverse <- solve(m)
cached_inverse <- cacheSolve(cache_m)
isTRUE(all.equal(direct_inverse, cached_inverse))

The second R script in the repository - performanceTest.R - can be used to determine the impact on performance of using the cached inverse of a matrix instead of computing it repeatedly with solve(). To test the difference in performance between cacheSolve() and solve() first download all R scripts in the current working directory of R/R Studio on your machine and then source the performanceTest.R script. Next, use the main function deltaTime() to measure the difference in performance between the two approaches of computing the inverse of a square matrix. The default values of the arguments used by the deltaTime() function are m_size = 100 - the size of the matrix to be used for computing the inverse (100x100) and iterations = 10, the number of times the inverse is computed using both approaches - direct and cached. Following is an example of the output of deltaTime() called without arguments (use the default values for the arguments):

  > source("performanceTest.R")
  > deltaTime()
   Number of iterations: 10 
   Matrix size: 100 x 100 
   Running time for 'solve()': 0.0190000000000001 sec.
   Running time for 'cacheSolve()': 0.00300000000000011 sec.
   Speed-up: 6.33333333333314 times

You can experiment with different matrix sizes by specifying the m_size argument and different number of iterations by specifying the
iterations argument.