From 16ec9c26067cc1693fcf31113dc2b3f13ecae9f2 Mon Sep 17 00:00:00 2001
From: "P.Fwu" <tramyeon@gmail.com>
Date: Sun, 20 Apr 2014 10:47:00 -0400
Subject: [PATCH] work done

---
 .Rhistory     | 19 +++++++++++++++++++
 cachematrix.R | 49 ++++++++++++++++++++++++++++++++++++++++++++-----
 cmd.R         |  7 +++++++
 3 files changed, 70 insertions(+), 5 deletions(-)
 create mode 100644 .Rhistory
 create mode 100644 cmd.R

diff --git a/.Rhistory b/.Rhistory
new file mode 100644
index 00000000000..ef6a4d983e1
--- /dev/null
+++ b/.Rhistory
@@ -0,0 +1,19 @@
+?solve
+m<-matrix(1:16, 4, 4)
+View(m)
+intm<-solve(m)
+rnorm(16)
+m<-matrix(rnorm(16)), 4, 4)
+m<-matrix(rnorm(16), 4, 4)
+intm<-solve(m)
+source('cachematrix.R')
+t1<- cacheSolve(m)
+source('cachematrix.R')
+t1 <- makeCacheMatrix(m)
+t1
+cacheSolve(t1)
+cacheSolve(makeCacheMatrix(m))
+solve(m)
+t1$get()
+t1$getInv()
+getwd()
diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..0bfee337216 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,54 @@
-## Put comments here that give an overall description of what your
-## functions do
+# implement cache to solve inverse matrix
+#
+# ex: 
+# my_matrix <- matrix(rnorm(16)), 4, 4)
+# my_inverse_matrix <- cacheSolve(makeCacheMatrix(my_matrix))
 
-## Write a short comment describing this function
+
+## Creat cache matrix with a list of four functions
 
 makeCacheMatrix <- function(x = matrix()) {
+        m <- NULL
+        
+        # set the matrix value
+        set <- function(y){
+                x <<- y
+                m <<- NULL
+        }
+        
+        # get matrix value
+        get <- function() x
+        
+        # set inverse matrix value
+        setInv <- function(im) m <<- im
+        
+        # get inverse matrix value
+        getInv <- function() m
+        list(set = set, get = get,
+             setInv = setInv,
+             getInv = getInv)
 
 }
 
 
-## Write a short comment describing this function
+## solve the inverse matirx from cache matrix
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+        # obtain inverse matrix, if not yet computed, NULL will be returned
+        m <- x$getInv()
+        
+        # if inverse matrix has been computed already, return the exisiting 
+        # result and end the function
+        if(!is.null(m)){
+                message("getting cached data")
+                return(m)
+        }
+        
+        # get matrix value
+        data <- x$get()
+        
+        # compute inverse matrix and return
+        m <- solve(data, ...)
+        x$setInv(m)
+        m
 }
diff --git a/cmd.R b/cmd.R
new file mode 100644
index 00000000000..564fe1348d9
--- /dev/null
+++ b/cmd.R
@@ -0,0 +1,7 @@
+m <- NULL
+set <- function(x) m <<-x
+
+set(2)
+
+##
+source('cachematrix.R')