Update cachematrix.R

programming assignment 2

Author: jfmichel

cachematrix.R

@@ -1,15 +1,36 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
+##  Creates a special "matrix" object that can cache its inverse.
+##  x : the matrix to encapsulate
+##  set(y) : set the matrix
+##  get : get the matrix
+##  setinverse(inverse) : set the inverse of the current matrix
+##  getinverse : retrieve the cached inverse matrix or NULL if no inverse matrix was set
 
 makeCacheMatrix <- function(x = matrix()) {
-
+   inv <- NULL
+   set <- function(y) {
+       x <<- y
+       inv <<- NULL
+   }
+   get <- function() x
+   setinverse <- function(inverse) inv <<- inverse
+   getinverse <- function() inv
+   list(set = set, get = get,
+        setinverse = setinverse,
+        getinverse = getinverse)   
 }
 
 
-## Write a short comment describing this function
+## Compute the inverse matrix of the CacheMatrix x.
+## This function returns the cached inverse matrix of x if it exists. 
+## If not it computes the inverse matrix of the encapsulated matrix of x and caches the result
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    ## Return a matrix that is the inverse of 'x'
+    inv <- x$getinverse()
+    if (!is.null(inv)) {
+        return(inv)
+    }
+    inv <- solve(x$get())
+    x$setinverse(inv)
+    inv
 }