Initial commit

Completed functions

Author: danhanley

cachematrix.R

@@ -1,15 +1,37 @@
-## Put comments here that give an overall description of what your
-## functions do
+## This file contains two functions 'makeCacheMatrix' and 'cacheSolve'
 
-## Write a short comment describing this function
+## makeCacheMatrix takes an ordinary matrix and extends it to allow 
+## the inverse to be stored in a cache
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  i <- NULL
+  set <- function(y) {
+    x <<- y
+    i <<- NULL
+  }
+  get <- function() x
+  setinv <- function(inv) i <<- inv
+  getinv <- function() i
+  list(set = set, get = get,
+       setinv = setinv,
+       getinv = getinv)
 }
 
 
-## Write a short comment describing this function
+## cacheSolve retrns the inverse of a matrix
+## It returns a cached value if one is stored, if not it:
+## calculates the inverse, stores it in the cache, and then returns it.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  ## Return a matrix that is the inverse of 'x'
+  i <- x$getinv()
+  if(!is.null(i)) {
+    message("getting cached data")
+    
+    return(i)
+  }
+  data <- x$get()
+  i <- solve(data, ...)
+  x$setinv(i)
+  i
 }