From 98f1946072a73b1c0c7c6316e380ed8e1383f483 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andrei=20Cus=CC=A7nir?= <cusnir@gmail.com>
Date: Sun, 18 Jan 2015 11:44:43 +0200
Subject: [PATCH] Updated cachematrix.R with implementation of functions
 makeCacheMatrix and cacheSolve

---
 cachematrix.R | 50 +++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 41 insertions(+), 9 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..69dbd836050 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,47 @@
-## Put comments here that give an overall description of what your
-## functions do
+# Coursera, R Programming(rprog-010), January 2015
+# Cache the inverse of a matrix
+# Matrix inversion is usually a costly computation and it makes sense 
+# to cache the inverse of a matrix rather than compute it repeatedly 
+# These two functions calculate and cache the inverse of a matrix.
 
-## Write a short comment describing this function
+## Example of usage
+## m <- matrix(c(4, 3, 3, 2), nrow = 2)
+## store the initial matrix in cached matrix object
+## m_cached <- makeCacheMatrix(m)
+## first call will solve the inverse and cache it
+## cacheSolve(m_cashed)
+## second call will return the cached value
+## cacheSolve(m_cashed)
 
+# This function creates an interface to access(get) and cache(set)
+# the contents of a matrix and the inverse of original matrix.
 makeCacheMatrix <- function(x = matrix()) {
-
+    inverse <- NULL
+    set <- function(y) {
+        x <<- y
+        inverse <<- NULL
+    }
+    get <- function() x
+    set_inverse <- function(inv) inverse <<- inv
+    get_inverse <- function() inverse
+    list(set = set, get = get,
+         set_inverse = set_inverse,
+         get_inverse = get_inverse)
 }
-
-
-## Write a short comment describing this function
-
+# This function computes the inverse of the special "matrix" 
+#  returned by makeCacheMatrix above.
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    ## Return a matrix that is the inv_matrix of 'x'
+    inverse <- x$get_inverse()
+    # check if inverse matrix was already calculated and 
+    # retrieve the content from the cache.
+    if(!is.null(inverse)) {
+        message("getting cached data")
+        return(inverse)
+    }
+    # else calculate the inverse matrix
+    data <- x$get()
+    inverse <- solve(data, ...)
+    x$set_inverse(inverse)
+    inverse
 }