completion of assignment

Author: Trent Albright

cachematrix.R

@@ -1,15 +1,56 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
-
-makeCacheMatrix <- function(x = matrix()) {
+## This module provides inverse operations for a matrix, but
+## improves performance by caching intermediary results
 
+## This function creates a special "matrix" object that can cache its inverse,
+## using the supported functions attached to the matrix object.
+##
+## create matrix: amatrix = makeCacheMatrix(matrix(c(1,2,3,4), nrow=2, ncol=2))
+## get matrix: amatrix$get()
+## set matrix: amatrix$set(matrix(c(0,5,99,66), nrow=2, ncol=2))
+## inverse of matrix: amatrix$getinverse()
+makeCacheMatrix <- function(self.matrix = matrix()) {
+  self.inv <- NULL
+  set <- function(newmatrix) {
+    self.matrix <<- newmatrix
+    self.inv <<- NULL
+  }
+  get <- function() {
+    self.matrix
+  }
+  getinverse <- function() {
+    self.inv
+  }
+  setinverse <- function(inverse) {
+    self.inv <<- inverse
+  }
+  list(set = set, get = get,
+       setinverse = setinverse,
+       getinverse = getinverse)  
 }
 
-
-## Write a short comment describing this function
-
-cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+## This function computes the inverse of the special "matrix" returned by 
+## vmakeCacheMatrix above. If the inverse has already been calculated (and 
+## the matrix has not changed), then cacheSolve retrieves the inverse from 
+## the cache.
+cacheSolve <- function(cachematrx, ...) {
+  inverse <- cachematrx$getinverse()
+  if(!is.null(inverse)) {
+    message("getting cached data")
+    return(inverse)
+  }
+  data <- cachematrx$get()
+  inverse <- solve(data, ...)
+  cachematrx$setinverse(inverse)
+  inverse
 }
+
+# mtrx = makeCacheMatrix(matrix(c(1,2,3,4), nrow=2, ncol=2))
+# mtrx$get()
+# cacheSolve(mtrx)
+# mtrx$getinverse()
+# cacheSolve(mtrx)
+# mtrx$set(matrix(c(0,5,99,66), nrow=2, ncol=2))
+# mtrx$get()
+# cacheSolve(mtrx)
+# mtrx$getinverse()
+# cacheSolve(mtrx)