From 4fc25fd84c05df8e85e9dd2123f8040d83129b14 Mon Sep 17 00:00:00 2001
From: ericmayor <eric.mayor@unine.ch>
Date: Mon, 21 Apr 2014 15:11:06 +0200
Subject: [PATCH] file edited for Prog assignment 2

---
 cachematrix.R | 47 +++++++++++++++++++++++++++++++++++------------
 1 file changed, 35 insertions(+), 12 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..6a683362d2e 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,38 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
-
-makeCacheMatrix <- function(x = matrix()) {
+# This function returns a list composed of a matrix of NAs called Inverse and functions that 
+# get:() returns the content of the matrix x submitted as argument of makeCacheMatrix
+# (set() of the original piece of code was not included because it was useless)
+# set_inverse() assigns the inverse of the matrix to the Inverse matrix using the special operator <<-
+# because Inverse is outside the environemnt of the function
+# get_inverse() returns the matrix Inverse
 
+makeCacheMatrix <- function(x) {
+	Inverse <- matrix (nrow = nrow(x), ncol = ncol(x))
+	get <- function() x
+	set_inverse <- function(Invs) {
+		Inverse <<- Invs
+		}
+	get_inverse <- function() {
+		Inverse
+	}
+	list(get = get, set_inverse = set_inverse,
+		get_inverse = get_inverse)
 }
 
-
-## Write a short comment describing this function
-
-cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
-}
+# This function returns the inverse of a matrix which was previously submitted as argument to the makeCacheMatrix function.
+# The argument for this function is a list returned by makeCacheMatrix().
+# The function first retrieves the matrix called Inverse from the list returned with makeCacheMatrix() using the function get_inverse of that list
+# It then checks if the first element is NA and if not prints 'Getting inverse of matrix' and returns the matrix (and the following code is not executed)
+# In case the first element of the matrix is actually an NA (meaning that the inverse of the matrix has not yet been computed), the function retrieves 
+# the content of the matrix originally submitted to makeCacheMatrix() and assigns it to  object M. It then assigns the inverse of M to Inverse.
+# It then assigns the object Inverse (in the scope of the function) to the Inverse object of the list submitted as argument, and finally returns the Inverse object.
+cacheSolve <- function(x) {
+	Inverse <- x$get_inverse()
+	if(!is.na(Inverse[1,1])) {
+		print("Getting inverse of matrix")
+		return(Inverse)
+	}
+	M <- x$get()
+	Inverse <- solve(M)
+	x$set_inverse(Inverse)
+	Inverse
+}
\ No newline at end of file