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‎cachematrix.R

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## Put comments here that give an overall description of what your
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## functions do
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## Write a short comment describing this function
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## This function creates and stores a special "matrix" object that can cache its inverse.
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## the object is a list of four functions
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makeCacheMatrix <- function(x = matrix()) {
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# store the value of the matrix
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m <- NULL
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set <- function(y) {
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x <<- y
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m <<- NULL
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}
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# retrieve the value of the matrix
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get <- function() x
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# store the value of the mean
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setInverse <- function(inverse) m <<- inverse
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# retrieve the value of the mean
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getInverse <- function() m
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# create and store the object: a list containing the 4 functions defined above
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list(set = set, get = get,
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setInverse = setInverse,
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getInverse = getInverse)
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}
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## Write a short comment describing this function
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## This function computes the inverse of a "matrix"
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## If the inverse has already been calculated (and the matrix has not changed), then the cachesolve retrieves the inverse from the cache.
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## Return a matrix that is the inverse of 'x'
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cacheSolve <- function(x, ...) {
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## Return a matrix that is the inverse of 'x'
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# first check to see if the inverse matrix has already been calculated and is cached
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inv <- x$getInverse()
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print(inv)
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if(!is.null(inv)) {
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message("Found in cache.")
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return(inv) # retrieve and return immediately
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} else
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{
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# not yet cached: calculate the inverse of the input matrix
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message("Not found in cache. Calculating it")
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data <- x$get()
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inv <- solve(data)
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# and set the value of the inverse matrix in the cache via the setInverse function.
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x$setInverse(inv)
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# return the calculated inverse matrix
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return(inv)
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}
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}
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## =========================================================================================
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## This function is used only to test that the above code is working as supposed
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##
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## Test basic caching
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##
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unitTestCacheMatrix <- function() {
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print("Start ... test matrix is: ")
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testMatrix <- matrix(c(1, 2, 3, 4), nrow=2, ncol=2)
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print(testMatrix)
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# Testing set() and get(): create the special matrix object with caching functions
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matrixCached <- makeCacheMatrix(testMatrix)
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print("Get. This is what has been cached: ")
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print (matrixCached$get())
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# Test cacheSolve(); now invert the test matrix
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inverseMatrix <- cacheSolve(matrixCached)
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print("The matrix inversed is: ")
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print (inverseMatrix)
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print("multiplying the test matrix with its inverse should return the identity matrix: ")
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print(testMatrix %*% inverseMatrix)
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# Test caching mechanism. Now calculating again. It should found it in the cache
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print("Now calculating again. It should found it in the cache")
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againMatrix <- cacheSolve(matrixCached)
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if (!identical(inverseMatrix, againMatrix))
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message("Cached version does not match solved version")
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}
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