From cafa9c7112fe0c2e50b90acb6c210dfb40724f84 Mon Sep 17 00:00:00 2001
From: Patrick McNeal <patrick.mcneal@gmail.com>
Date: Tue, 22 Apr 2014 14:24:02 -0400
Subject: [PATCH] Add initial solution with comments.

---
 cachematrix.R | 53 ++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 46 insertions(+), 7 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..19cb0c1707d 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,54 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
+## This function creates a special "matrix" object that can cache its inverse.
 
 makeCacheMatrix <- function(x = matrix()) {
+    inverse <- NULL
 
+    # Set matrix value and delete cached inverse only if new matrix is
+    # different than current value
+    set <- function(y) {
+        if (!identical(x, y)) {
+            x <<- y
+            inverse <<- NULL
+        }
+    }
+    
+    # Return current matrix value
+    get <- function() x
+    
+    # Cache inverse value
+    setinverse <- function(solve) inverse <<- solve
+    
+    # Return cached inverse value
+    getinverse <- function() inverse
+    
+    list(set = set, get = get,
+         setinverse = setinverse,
+         getinverse = getinverse)
 }
 
 
-## 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 cacheSolve retrieves the inverse from the 
+## cache.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
-}
+    
+    # Return cached inverse value if one is found
+    inverse <- x$getinverse()
+    if(!is.null(inverse)) {
+        message("getting cached data")
+        return(inverse)
+    }
+    
+    # No cached inverse, so need to calculate
+    message("cached data not found, calculating value")
+    data <- x$get()
+    inverse <- solve(data, ...)
+    
+    # Cache inverse matrix for future use
+    x$setinverse(inverse)
+    
+    # Return inverse matrix
+    inverse
+}
\ No newline at end of file