From b37c927fe8aa5006c140f3ca3b9940a54198b441 Mon Sep 17 00:00:00 2001
From: happyB <bfoth@gmx.net>
Date: Sun, 13 Apr 2014 17:34:45 +0100
Subject: [PATCH 1/4] Added a comment

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

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..becb6ed17ae 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -2,6 +2,7 @@
 ## functions do
 
 ## Write a short comment describing this function
+# A function that can create a 'matrix' object that is capable of caching its own inverse
 
 makeCacheMatrix <- function(x = matrix()) {
 

From 269d6c52627e9d9f5fe21eaac587768d65a02102 Mon Sep 17 00:00:00 2001
From: happyB <bfoth@gmx.net>
Date: Sat, 26 Apr 2014 18:05:53 +0100
Subject: [PATCH 2/4] The frist change in this file, adding 2 letters

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

diff --git a/cachematrix.R b/cachematrix.R
index becb6ed17ae..4bce63c4f63 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,5 +1,5 @@
 ## Put comments here that give an overall description of what your
-## functions do
+## functions do BF
 
 ## Write a short comment describing this function
 # A function that can create a 'matrix' object that is capable of caching its own inverse

From 5d6867e4425afc633e9960ccbb970a834fae806b Mon Sep 17 00:00:00 2001
From: happyB <bfoth@gmx.net>
Date: Sat, 26 Apr 2014 18:54:55 +0100
Subject: [PATCH 3/4] R code fully implemented and commented

---
 cachematrix.R | 45 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index 4bce63c4f63..5216cc60aae 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,16 +1,41 @@
-## Put comments here that give an overall description of what your
-## functions do BF
-
-## Write a short comment describing this function
-# A function that can create a 'matrix' object that is capable of caching its own inverse
+## A matrix inversion is a complex mathematical operation 
+## (see e.g. http://www.purplemath.com/modules/mtrxinvr.htm).
+## The following two functions are meant to allow the repeated determination of the result
+## of a matrix inversion, BUT if an inverse of a matrix has been calculated once and the original
+## matrix has not changed, the functions will return the CACHED inverse of the original matrix,
+## thereby saving computation time.
 
+# The makeCacheMatrix function creates a 'matrix' object, which in reality is a LIST containing a function
+# that defines 4 different calls (set, get, setinverse, getinverse). This function expects to be passed a
+# "real" matrix object.
 makeCacheMatrix <- function(x = matrix()) {
-
+  i <- NULL
+  set <- function(y) {
+    x <<- y
+    i <<- NULL
+  }
+  get <- function() x
+  setinverse <- function(solved) i <<- solved
+  getinverse <- function() i
+  list(set = set, get = get,
+       setinverse = setinverse,
+       getinverse = getinverse)
 }
 
-
-## Write a short comment describing this function
-
+# The cacheSolve function calculates the inverse of the "matrix" created by the makeCacheMatrix function.
+# It first checks whether the inverse has already been calculated for the original matrix, and if it has
+# (without the original matrix having been re-set in the meantime) it simply returns the cached inverse
+# of the matrix, without new calculation. If the inverse of the matrix is not stored in the 
+# makeCacheMatrix function, the cacheSolve function will calculate it and cache the result in the 
+# makeCacheMatrix function.
 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
 }

From f2dbbd31175c5935657b726391d6bdfc098df41c Mon Sep 17 00:00:00 2001
From: happyB <bfoth@gmx.net>
Date: Sat, 26 Apr 2014 21:37:24 +0100
Subject: [PATCH 4/4] R code fully implemented and commented - minor update

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

diff --git a/cachematrix.R b/cachematrix.R
index 5216cc60aae..0e806992e11 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -15,7 +15,7 @@ makeCacheMatrix <- function(x = matrix()) {
     i <<- NULL
   }
   get <- function() x
-  setinverse <- function(solved) i <<- solved
+  setinverse <- function(inverse) i <<- inverse
   getinverse <- function() i
   list(set = set, get = get,
        setinverse = setinverse,