From 4e417596fc9a67b1834a0c24975424ff179b5ce5 Mon Sep 17 00:00:00 2001
From: Hsing Liu <liu.hsing@gmail.com>
Date: Sat, 12 Apr 2014 15:31:57 +0800
Subject: [PATCH 1/2] first commit

---
 draft.R | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 draft.R

diff --git a/draft.R b/draft.R
new file mode 100644
index 00000000000..1d8100714c8
--- /dev/null
+++ b/draft.R
@@ -0,0 +1,52 @@
+makeCacheMatrix <- function(x = matrix()) {
+	## Creates a list of functions used to cache/store
+	## a matrix and its inverse
+	## Usage example:
+	##	m <- makeCacheMatrix(matrix(1:4, 2, 2))
+	##	...
+	##	m$set(matrix(c(1, -1, 0, 1), 2, 2))
+
+
+	# Inverse matrix is initiated with NULL value
+        inverse <- NULL
+
+	# Set/get functions
+        set <- function(y) {
+                x <<- y
+                inverse <<- NULL
+        }
+        get <- function() x
+        setinverse <- function(solved) inverse <<- solved
+        getinverse <- function() inverse
+
+	# Return the functions as a list
+        list(set = set, get = get,
+             setinverse = setinverse,
+             getinverse = getinverse)
+}
+
+cacheSolve <- function(x, ...) {
+	## Calculate the inverse of a matrix, using makeCacheMatrix
+	## to "cache" the inverse.  That is, if the inverse had
+	## been calculated previously, then get the saved inverse
+	## and return it.
+	##
+	## Usage example:
+	##	m <- makeCacheMatrix(...)
+	##	cacheSolve(m)
+
+
+	# Check if there is a previously calculated inverse
+	# If there is, then return the inverse (and exit function)
+        inverse <- x$getinverse()
+        if(!is.null(inverse)) {
+                message("Getting cached inverse matrix")
+                return(inverse)
+        }
+
+	# Calculate and store inverse
+        data <- x$get()
+        inverse <- solve(data, ...)
+        x$setinverse(inverse)
+        inverse
+}

From 92c48c05f5af638f9e8b950ffb34ed2a6df3fd25 Mon Sep 17 00:00:00 2001
From: Hsing Liu <liu.hsing@gmail.com>
Date: Sat, 12 Apr 2014 15:42:30 +0800
Subject: [PATCH 2/2] draft work integrated into cachematrix.R

---
 cachematrix.R | 51 +++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..0e1585fd80c 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,58 @@
-## Put comments here that give an overall description of what your
-## functions do
 
-## Write a short comment describing this function
+## makeCacheMatrix() creates a vector to cach a matrix and its inverse
+## cacheSolve takes a cached matrix created by makeCacheMatrix and
+## return its inverse
+
+
+## makeCacheMatrix() creates a list of functions used to cache/store
+## a matrix and its inverse
+## Usage example:
+##	m <- makeCacheMatrix(matrix(1:4, 2, 2))
+##	...
+##	m$set(matrix(c(1, -1, 0, 1), 2, 2))
 
 makeCacheMatrix <- function(x = matrix()) {
+	# Inverse matrix is initiated with NULL value
+        inverse <- NULL
+
+	# Set/get functions
+        set <- function(y) {
+                x <<- y
+                inverse <<- NULL
+        }
+        get <- function() x
+        setinverse <- function(solved) inverse <<- solved
+        getinverse <- function() inverse
 
+	# Return the functions as a list
+        list(set = set, get = get,
+             setinverse = setinverse,
+             getinverse = getinverse)
 }
 
 
-## Write a short comment describing this function
+## cacheSolve calculates the inverse of a matrix, using makeCacheMatrix
+## to "cache" the inverse.  That is, if the inverse had been calculated
+## previously, then get the saved inverse and return it.
+##
+## Usage example:
+##	m <- makeCacheMatrix(...)
+##	cacheSolve(m)
 
 cacheSolve <- function(x, ...) {
         ## Return a matrix that is the inverse of 'x'
+
+	# Check if there is a previously calculated inverse
+	# If there is, then return the inverse (and exit function)
+        inverse <- x$getinverse()
+        if(!is.null(inverse)) {
+                message("Getting cached inverse matrix")
+                return(inverse)
+	}
+
+	# Calculate and store inverse
+        data <- x$get()
+        inverse <- solve(data, ...)
+        x$setinverse(inverse)
+        inverse
 }