Update cachematrix.R

Author: GillesD

cachematrix.R

@@ -1,15 +1,39 @@
-## Put comments here that give an overall description of what your
-## functions do
+# Excuse me for my English. I'm french student!!!
 
-## Write a short comment describing this function
+# Matrix inversion is expensive in computational time. For better performance,
+# the inverse of the matrix is cached (no need to recalculate it each time)
+# The finctions makeCacheMatrix.R and cacheResolve.R are used to do this
 
-makeCacheMatrix <- function(x = matrix()) {
+# set matrix value
+# get matrix value
+# set inverse matrix value
+# get inverse matrix value
 
+makeCacheMatrix <- function(x = matrix()) {
+  xInv <- NULL
+  fixer <- function(y) {
+    x <<- y
+    xInv <<- NULL
+  }
+  obtenir <- function() x
+  fixerInverse <- function(inverse) xInv <<- inverse
+  obtenirInverse <- function() xInv
+  list(fixer=fixer, obtenir=obtenir, fixerInverse=fixerInverse, obtenirInverse=obtenirInverse)
 }
 
 
-## Write a short comment describing this function
-
+# cacheSolve.R return matrix inverse value
+# It first checks if the inverse of the matrix has already been computed and is in the
+# cache. If so, it retrieves the value and skips the calculation.
+# Otherwise, it calculates the inverse of the matrix and stores the value in the cache.
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+ inv <- x$obtenirInverse()
+  if(!is.null(inv)) {
+    message("Obtenir les donnees en cache.")
+    return(inv)
+  }
+  donnee <- x$obtenir()
+  inv <- solve(donnee)
+  x$fixerInverse(inv)
+  inv
 }