filled in the assignment code. created memoized method call and special 'cache' solve for matrix

Author: scoroberts

cachematrix.R

@@ -1,15 +1,48 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Taking the inverse of a matrix can be a very expensive operation
+## for very large matricies. These methods allow one to cache
+## the expensive operation so that if called again, the value
+## will be retuned much faster.  This technique is also known
+## as memoization in computer science.
+##
+## Example:
+##   > testm <- makeCacheMatrix(matrix(c(2:5),2,2))
+##   > cacheSolve(testm)    #expensive operation
+##   > cacheSolve(testm)    #cache hit on second run
 
-## Write a short comment describing this function
 
-makeCacheMatrix <- function(x = matrix()) {
+## This function will create a special version of matrix
+## which will encapsulate the matrix value as well as the
+## inverse of the matrix. This contains getters and setters
+## for these values.
 
+makeCacheMatrix <- function(x = matrix()) {
+    inv <- NULL
+    set <- function(y) {
+        x <<- y
+        inv <<- NULL
+    }
+    get <- function() x
+    setinv <- function(i) inv <<- i
+    getinv <- function() inv
+    
+    list(set = set, get = get,
+         setinv = setinv,
+         getinv = getinv)
 }
 
 
-## Write a short comment describing this function
+## This will check to see if there is a cached inverse value.
+## If not found, the inverse will be calculated, caached and
+## returned.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    inv <- x$getinv()
+    if (!is.null(inv)) {
+        message("cache hit")
+        return(inv)
+    }
+    data <- x$get()
+    inv <- solve(data, ...)
+    x$setinv(inv)
+    inv
 }