From 2c893bf16ce8671529b843ba044cc5da9e702066 Mon Sep 17 00:00:00 2001
From: tim Lantz <tim.lantz@gmail.com>
Date: Sun, 13 Apr 2014 17:36:26 -0400
Subject: [PATCH 1/3] adding cached matrix functions

---
 cachematrix.R | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..a4f099c4db0 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -4,12 +4,33 @@
 ## Write a short comment describing this function
 
 makeCacheMatrix <- function(x = matrix()) {
-
+    inv <- NULL
+    set <- function(omx) {
+        mx <<- omx
+        inv <<- NULL
+    }
+    get <- function() x
+    setinverse <- function(inverse) inv <<-inverse
+    getinverse <- function() inv
+    list(
+        set = set,
+        get = get
+        setinverse = setinverse,
+        getinverse = getinverse
+    )
 }
 
 
 ## Write a short comment describing this function
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    inv <- x$getinverse()
+    if (!is.null(inv)) {
+        message('getting cached inverse')
+    } else {
+        data <- x$get()
+        inv <- solve(data, ...)
+        x$setinverse(inv)
+    }
+    inv
 }

From 285282e1f114e947892fddc15f1b098c9acd6138 Mon Sep 17 00:00:00 2001
From: tim Lantz <tim.lantz@gmail.com>
Date: Sun, 13 Apr 2014 17:36:49 -0400
Subject: [PATCH 2/3] fixing missing comma

---
 cachematrix.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cachematrix.R b/cachematrix.R
index a4f099c4db0..ee4c11f6e4f 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -14,7 +14,7 @@ makeCacheMatrix <- function(x = matrix()) {
     getinverse <- function() inv
     list(
         set = set,
-        get = get
+        get = get,
         setinverse = setinverse,
         getinverse = getinverse
     )

From 288836f4847b579bc334272ab069b6c5360a80e2 Mon Sep 17 00:00:00 2001
From: tim Lantz <tim.lantz@gmail.com>
Date: Sun, 13 Apr 2014 18:01:56 -0400
Subject: [PATCH 3/3] commenting and fixing bad variable name in set

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

diff --git a/cachematrix.R b/cachematrix.R
index ee4c11f6e4f..6f00d8da975 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,16 +1,35 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
+## Functions for wrapping a matrix with inverse caching functionality as specified by
+## programming assignment 2 of the R Programming Coursera course.
+##
+## makeCacheMatrix  wraps a regular matrix with cache goodness
+## cacheSolve       wrapper for solve() that leverages caching functionality
+##
+## Note: Google commenting style followed (function comments below first line).
+## See http://google-styleguide.googlecode.com/svn/trunk/Rguide.xml. 
 
 makeCacheMatrix <- function(x = matrix()) {
+    # Wraps a matrix with capabilities to cache its inverse.
+    #
+    # Args:
+    #   x: An matrix (assumed to be invertible). Default is the empty matrix.
+    #
+    # Returns:
+    #   A list with accessors for the matrix as follows. 
+    #
+    #   v.set(x)            sets the underlying matrix (clears the cache)
+    #   v.get()             retrieves the underlying matrix
+    #   v.setinverse(xp)    sets the inverse cache
+    #   v.getinverse()      gets the the cached inverse or NULL if not set
+
+    # inv will be the variable for storing the cached inverse
     inv <- NULL
     set <- function(omx) {
-        mx <<- omx
+        # the matrix has changed, wipe out the inverse as well
+        x <<- omx
         inv <<- NULL
     }
     get <- function() x
-    setinverse <- function(inverse) inv <<-inverse
+    setinverse <- function(inverse) inv <<- inverse
     getinverse <- function() inv
     list(
         set = set,
@@ -20,17 +39,30 @@ makeCacheMatrix <- function(x = matrix()) {
     )
 }
 
-
-## Write a short comment describing this function
-
 cacheSolve <- function(x, ...) {
+    # Computers or fetches the cached inverse of x. 
+    #
+    # Args:
+    #   x:   A wrapped matrix with caching functionality created with 
+    #        createCacheMatrix.
+    #   ...: Extra arguments for solve. Note that these arguments will not get recheceked
+    #        when accessing the cache. In other words two calls with different "..." args
+    #        will get you the same matrix. This is consistent with the assignment vector
+    #        example.
+    #
+    # Returns:
+    #   The inverse of x's underlying matrix. 
     inv <- x$getinverse()
     if (!is.null(inv)) {
+        # like the vector example, show a message when we get from cache
+        # inv already points to the cached inverse
         message('getting cached inverse')
     } else {
+        # compute inv and cache it
         data <- x$get()
         inv <- solve(data, ...)
         x$setinverse(inv)
     }
     inv
 }
+