From 67fd9a71e817ce60cb1fa2d112c074a228ef4064 Mon Sep 17 00:00:00 2001
From: Steve Knight <steve@hackinghat.com>
Date: Mon, 15 Sep 2014 08:50:02 +0100
Subject: [PATCH 1/2] Update cachematrix.R

Initial version
---
 cachematrix.R | 43 +++++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..fb875609d53 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,38 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
-
+## Make a cache matrix with an initially unset inverse
 makeCacheMatrix <- function(x = matrix()) {
-
+  # Inverse is initially null
+  i <- NULL
+  set <- function(y) {
+    # Set the data and the inverse into the parent scope
+    x <<- y
+    i <<- NULL
+  }
+  # Get the value of the matrix
+  get <- function() x
+  # Set the *cached* inverse of the matrix
+  setinv <- function(inv) i <<- inv
+  # Get the *cached* inverse of the matrix
+  getinv <- function() i
+  # Return a named-list with the data and functions embedded in it
+  list(set = set, get = get,
+       setinv = setinv,
+       getinv = getinv)
 }
 
-
-## Write a short comment describing this function
-
+## Memoize the solve function so as to provide a cached version of the inverse, if available, otherwise
+## calculate, cache and return the inverse.
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  # If the inverse is already calculated return it 
+  i <- x$getinv()
+  if (!is.null(i)) {
+    message("getting cached data")
+    return(i)
+  }
+  # Retrieve the data from the 'matrix'
+  data <- x$get()
+  # Solve the matrix to retrieve the inverse
+  i <- solve(data, ...)
+  x$setinv(i)
+  i
 }
+

From 6e30e64560f8227c1bf77f688e08fb6d3e1cca2c Mon Sep 17 00:00:00 2001
From: Steve Knight <steve@hackinghat.com>
Date: Mon, 15 Sep 2014 08:51:32 +0100
Subject: [PATCH 2/2] Changed comments

---
 cachematrix.R | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index fb875609d53..b103d0f4918 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,4 +1,4 @@
-## Make a cache matrix with an initially unset inverse
+## Make a cached 'matrix' with an initially unset inverse
 makeCacheMatrix <- function(x = matrix()) {
   # Inverse is initially null
   i <- NULL
@@ -22,7 +22,7 @@ makeCacheMatrix <- function(x = matrix()) {
 ## Memoize the solve function so as to provide a cached version of the inverse, if available, otherwise
 ## calculate, cache and return the inverse.
 cacheSolve <- function(x, ...) {
-  # If the inverse is already calculated return it 
+  # Get the inverse, if the inverse is already calculated return it 
   i <- x$getinv()
   if (!is.null(i)) {
     message("getting cached data")
@@ -30,8 +30,9 @@ cacheSolve <- function(x, ...) {
   }
   # Retrieve the data from the 'matrix'
   data <- x$get()
-  # Solve the matrix to retrieve the inverse
+  # Solve the matrix to retrieve the inverse, passing the additional options from the caller
   i <- solve(data, ...)
+  # Store the result
   x$setinv(i)
   i
 }