submit assignment 02

Author: whkoh

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
+## Date:    19 January 2015
+## Course:  R Programming 
+##
+## Testing procedures
+## Step 1: q <- makeCacheMatrix()
+## Step 2: q$set(matrix(1:9,3,3))
+## Step 3: cacheSolve(q)
+## This returns the inverse of the matrix and caches it.
+## Step 4: cacheSolve(q)
+## This returns the cached solution with a message 'Getting cached data!'
+##
+## makeCacheMatrix function description 
+##
+## makeCacheMatrix is a function that creates a 'matrix' object
+## that can cache its inverse. Solving is not handled here.
+## makeCacheMatrix saves the matrix to variable x and its inverse
+## to m. The returned list contains: 
+## set: sets matrix & resets cache of inverse
+## get: returns matrix
+## setsolution: saves solve value
+## getsolution: returns cached inverse value
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  m <- NULL
+  set <- function (y) {
+    x <<- y
+    m <<- NULL
+  }
+  get <- function() x
+  setsolution <- function(solve) m <<- solve
+  getsolution <- function() m
+  list(set = set, get = get, 
+         setsolution = setsolution, getsolution = getsolution
+       )
 }
+## cacheSolve function description
+##
+## cacheSolve is a function to get inversed matrix from 
+## the object created by the previous function. It takes
+## the object as argument x, and checks if the inverse value is 
+## already cached. If cached, it returns the cached value. If
+## not cached, it calculates the inverse for the matrix in x
+## and saves into the x cache using setsolution. The result
+## is then returned.
 
-
-## Write a short comment describing this function
-
-cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+cacheSolve <- function(x=matrix(), ...) {
+  m<-x$getsolution()
+  if(!is.null(m)) {
+    message("Getting cached data!")
+    return(m)
+  }
+  matrix <- x$get()
+  m <- solve(matrix, ...)
+  x$setsolution(m)
+  m
 }