initial design

calvins · calvins · commit feebd0118029 · 2015-05-11T10:58:44.000-04:00
diff --git a/cachematrix.R b/cachematrix.R
@@ -2,14 +2,49 @@
 ## functions do
 
 ## Write a short comment describing this function
+makeCacheMatrix is a function that creates a special matrix that can be used to cache
+its inverse, since matrix inversion can be time consuming.  Instead of recalculating
+the inverse of a matrix, it will be stored in a cache for retrieval.
 
-makeCacheMatrix <- function(x = matrix()) {
+makeCacheMatrix returns a list with a function to 
+1.  set the value of the matrix
+2.  get the value of the matrix
+3.  set the value of the matrix inverse
+4.  get the value of the matrix inverse
 
+makeCacheMatrix <- function(x = matrix()) {
+    m <- NULL
+    set <- function(y) {
+        x <<- y
+        m <<- NULL
+    }
+    get <- function() x
+    setmatrixInverse <- function(calcMatrixInverse) m <<- matrixInverse
+    getmatrixInverse <- function() m
+    list(set = set, get = get,
+         setmatrixInverse = setmatrixInverse,
+         getmatrixInverse = getmatrixInverse)
 }
 
 
 ## Write a short comment describing this function
 
+The following function calculates the matrix inverse of the special "vector"
+created with the above function. However, it first checks to see if the
+matrix inverse has already been calculated. If so, it `get`s the matrix inverse from the
+cache and skips the computation. Otherwise, it calculates the matrix inverse of
+the data and sets the value of the matrix inverse in the cache via the `setMatrixInverse`
+function.
+
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    ## Return a matrix that is the inverse of 'x'
+    m <- x$matrixInverse()
+    if(!is.null(m)) {
+        message("getting cached data")
+        return(m)
+    }
+    data <- x$get()
+    m <- calcMatrixInverse(data, ...)
+    x$setmatrixInverse(m)
+    m
 }
