Initial implementation of makeCacheMatrix and cacheSolve functions

Author: mattlangeman

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
+## makeCacheMatrix is a function that creates a special "matrix" object 
+## that can cache its inverse.
 
 makeCacheMatrix <- function(x = matrix()) {
-
+    inverse_x <- NULL
+    set <- function(y) {
+        x <<- y
+        inverse_x <<- NULL
+    }
+    get <- function() x
+    set_inverse <- function(inverse) inverse_x <<- inverse
+    get_inverse <- function() inverse_x
+    list(set = set, get = get,
+         set_inverse = set_inverse,
+         get_inverse = get_inverse)
 }
 
 
-## Write a short comment describing this function
+## cacheSolve is a function that computes the inverse of the special "matrix"
+## returned by makeCacheMatrix above. 
+## If the inverse has already been calculated (and the matrix has not changed), 
+## then cacheSolve should retrieve the inverse from the cache.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
-}
+    ## Return a matrix that is the inverse of 'x'
+    inverse_x = x$get_inverse()
+    if (! is.null(inverse_x)) {
+        message("getting cached data")
+        return(inverse_x)
+    }
+    data <- x$get()
+    inverse_x <- solve(data, ...)
+    x$set_inverse(inverse_x)
+    inverse_x
+}