From 2514d8491898cef7c1a2ccc5ef80f800db234191 Mon Sep 17 00:00:00 2001
From: hoangh <hoangh@users.noreply.github.com>
Date: Tue, 22 Apr 2014 19:46:37 +1000
Subject: [PATCH] Update cachematrix.R

---
 cachematrix.R | 62 ++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 57 insertions(+), 5 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..3c2095d366b 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,67 @@
-## Put comments here that give an overall description of what your
-## functions do
+# ===============================================================================================
+# ===============================================================================================
+# ===============================================================================================
 
-## Write a short comment describing this function
+# makeCacheMatrix function creates a special "matrix" object that can cache its inverse
+# It contains a list of functions as follow:
+# set the value of the input matrix
+# get the value of the input matrix
+# set the value of the inverse matrix
+# get the value of the inverse matrix
 
 makeCacheMatrix <- function(x = matrix()) {
+    # initialize inverse matrix
+    inv <- NULL
 
+    # set matrix value
+    set <- function(y) {
+        x <<- y
+        inv <<- NULL   
+    }
+    
+    # get matrix value 
+    get <- function() x
+    # set inverse matrix
+    setinv <- function(inv_) inv <<- inv_
+    # get inverse matrix
+    getinv <- function() inv
+
+    # list of all functions
+    list(set = set, get = get,
+         setinv = setinv,
+         getinv = getinv)    
 }
 
 
-## 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 the cachesolve 
+# should retrieve the inverse from the cache.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    # if the inverse is already exist then cache
+    inv <- x$getinv()
+    if(!is.null(inv)) {
+        message("getting cached data")
+        return(inv)
+    }
+    
+    data <- x$get()
+    
+    # Calculate inverse matrix using solve function
+    inv <- solve(data, ...)
+    
+    # cache that inverse matrix
+    x$setinv(inv)
+    
+    # return 
+    inv
 }
+
+# ===============================================================================================
+# ===============================================================================================
+# ===============================================================================================
+