Completed and tested the 2 functions

Completed and tested the 2 functions.
Used system.time to compare speed of solve vs cacheSolve
on a 10x10 matrix.
cacheSolve was (only) 12 times faster¬!

Author: miktro

cachematrix.R

@@ -1,15 +1,35 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
-
-makeCacheMatrix <- function(x = matrix()) {
-
-}
-
-
-## Write a short comment describing this function
-
-cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
-}
+## Put comments here that give an overall description of what your
+## functions do
+
+## This creates a new object that stores a matrix 
+## together with it's inverse - initially set to NULL
+
+makeCacheMatrix <- function(x = matrix()) {
+    mi <- NULL
+    set <- function(y) {
+        x <<- y
+        mi <<- NULL
+    }
+    get <- function() x
+    setinverse <- function(inv) mi <<- inv
+    getinverse <- function() mi
+    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'
+    mi <- x$getinverse()
+    if(!is.null(mi)) {
+        #message("getting cached matrix inverse")
+        return(mi)
+    }
+    data <- x$get()
+    mi <- solve(data, ...)
+    x$setinverse(mi)
+    mi
+}