Completed assignment

Author: jonathanbona

cachematrix.R

@@ -1,15 +1,42 @@
-## Put comments here that give an overall description of what your
-## functions do
+## These functions take advantage of R's scoping rules to "cache" potentiall expensive 
+## matrix inverse operations
 
-## Write a short comment describing this function
 
-makeCacheMatrix <- function(x = matrix()) {
 
+## makeCacheMatrix creates a special "matrix", which is a list of functions to:
+## set the value of the matrix
+## get the value of the matrix
+## set the value of the matrix's inverse
+## get the value of the matrix's inverse
+makeCacheMatrix <- function(x = matrix()) {
+  i <- NULL
+  
+  set <- function(y){
+    x <<- y
+    i <<- NULL
+  }
+  get <- function() x
+  setinverse <- function(inverse) i <<- inverse
+  getinverse <- function() i
+  # returns a list of these functions
+  list(set = set, get = get, setinverse = setinverse, getinverse = getinverse)
 }
 
 
-## Write a short comment describing this function
-
+## Calculates the inverse of a "matrix" created by makeCacheMatrix
+## If the inverse has already been calculated and cached, return it. 
+## Otherwise: calcaulate, cache, and return it.
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+ ## Return a matrix that is the inverse of 'x'
+  i <- x$getinverse()
+  # already cached? return it
+  if(!is.null(i)){
+    message("getting cached inverse")
+    return(i)
+  }
+
+  data <- x$get() # get the matrix
+  i <- solve(data) # calculate its inverse
+  x$setinverse(i) # cache the inverse
+  i # return it
 }