implemented the functions makeCacheMatrix() and cacheSolve()

Author: ptuzla

cachematrix.R

@@ -1,15 +1,72 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Matrix inversion is usually a costly computation and there may be some benefit 
+## to caching the inverse of a matrix rather than computing it repeatedly. 
+## These two functions, makeCacheMatrix() and cacheSolve() are used to cache the
+## inverse of a matrix
 
-## Write a short comment describing this function
+## This function creates a special "matrix" object that can cache its inverse
 
 makeCacheMatrix <- function(x = matrix()) {
-
+    i <- NULL
+    set <- function(y) {
+        x <<- y
+        i <<- NULL
+    }
+    get <- function() x
+    setinverse <- function(inv) i <<- inv
+    getinverse <- function() i
+    list(set = set, get = get,
+         setinverse = setinverse,
+         getinverse = getinverse)
 }
 
 
-## Write a short comment describing this function
+## This function computes the inverse of the special "matrix" returned by 
+## makeCacheMatrix above. If the inverse has already been calculated 
+## (and the matrix has not changed), then cacheSolve should retrieve the 
+## inverse from the cache
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    i <- x$getinverse()
+    if(!is.null(i)) {
+        message("getting cached data")
+        return(i)
+    }
+    data <- x$get()
+    i <- solve(data, ...)
+    x$setinverse(i)
+    i
 }
+
+# Sample output
+# 
+# > cacheMatrix = makeCacheMatrix(m1)
+# > print(cacheSolve(cacheMatrix))
+# [,1] [,2]
+# [1,]  0.6 -0.2
+# [2,] -0.7  0.4
+# > print(cacheSolve(cacheMatrix))
+# getting cached data
+# [,1] [,2]
+# [1,]  0.6 -0.2
+# [2,] -0.7  0.4
+# > print(cacheSolve(cacheMatrix))
+# getting cached data
+# [,1] [,2]
+# [1,]  0.6 -0.2
+# [2,] -0.7  0.4
+# >
+# > cacheMatrix$set(m2)
+# > print(cacheSolve(cacheMatrix))
+# [,1] [,2]
+# [1,]  0.3 -0.1
+# [2,] -0.1  0.1
+# > print(cacheSolve(cacheMatrix))
+# getting cached data
+# [,1] [,2]
+# [1,]  0.3 -0.1
+# [2,] -0.1  0.1
+# > print(cacheSolve(cacheMatrix))
+# getting cached data
+# [,1] [,2]
+# [1,]  0.3 -0.1
+# [2,] -0.1  0.1