From 6f39b693d451bda7a0d0d9f1b6f17242f350aa91 Mon Sep 17 00:00:00 2001
From: David Meisner <david.b.meisner@gmail.com>
Date: Mon, 14 Apr 2014 17:37:30 -0400
Subject: [PATCH] first commit

---
 cachematrix.R | 42 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 6 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..c6872e15d97 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,45 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Matrix inversion can be a costly computation. We have therefore created a pair of functions
+## which enable caching of the matrix inversion, such that it may be retrieved without repeated 
+## computations. 
+## Note: These functions assume that the provided matrix is square and invertible.
 
-## Write a short comment describing this function
 
-makeCacheMatrix <- function(x = matrix()) {
+## This function creates a special "matrix" object that can cache its inverse.
+## It is actually a list which can:
+## 1) Set the value of the matrix
+## 2) Get the value of the matrix
+## 3) Set the value of the matrix inverse
+## 4) Get the value of the matrix inverse
 
+makeCacheMatrix <- function(x = matrix()) {
+  inv <- NULL
+  set <- function(y) {
+    x <<- y
+    inv <<- NULL
+  }
+  get <- function() x
+  setInv <- function(solve) inv <<- solve
+  getInv <- function() inv
+  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), it gets
+## the inverse from the cache and skips the computation. Otherwise, it computes the inverse and sets
+## the value of the inverse in the cache.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  ## Return a matrix that is the inverse of 'x'
+  inv <- x$getInv()
+  if(!is.null(inv)) {
+    message("getting cached data")
+    return(inv)
+  }
+  mat <- x$get()
+  inv <- solve(mat)
+  x$setInv(inv)
+  inv
 }