From 432f25aa8758ad7dc18b584fd0aa51173a1d29c2 Mon Sep 17 00:00:00 2001
From: maxeywen <mobiwen@gmail.com>
Date: Mon, 28 Apr 2014 10:21:25 +0800
Subject: [PATCH] Update cachematrix.R

completed functions
  makeCacheMatrix()
  cacheSolve()
added comments
---
 cachematrix.R | 43 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..349a39b8c98 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,44 @@
-## Put comments here that give an overall description of what your
-## functions do
+## 2 functions that will accept a matrix, calculate its inverse, cache the result,
+## and return the cached inverse unless the original matrix is changed
 
-## Write a short comment describing this function
+## makeCacheMatrix()
+## exposes 4 methods in a list
+## set, get, setInverse, getInverse
 
 makeCacheMatrix <- function(x = matrix()) {
-
+    i <- NULL
+    
+    set <- function(y) {
+        x <<- y
+        i <<- NULL
+    }
+    
+    get <- function() x
+    
+    setInverse <- function(inv) i <<- inv
+    
+    getInverse <- function() i
+    
+    list(set = set, get = get,
+         setInverse = setInverse,
+         getInverse = getInverse)
 }
 
 
-## Write a short comment describing this function
+## checks cache first for inverse.  if cache is NULL,
+## solves the matrix and stores in cache
 
-cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+cacheSolve <- function(x) {
+    ## Return a matrix that is the inverse of 'x'
+  
+    i <- x$getInverse()
+    if(!is.null(i)) {
+        message("getting cached data")
+        return(i)
+    }
+    
+    data <- x$get()
+    i <- solve(data)
+    x$setInverse(i)
+    i
 }