commit and submit cachematrix.R

tff626 · tff626 · commit c0de414faf42 · 2014-04-19T22:44:08.000-07:00
diff --git a/cachematrix.R b/cachematrix.R
@@ -1,15 +1,57 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Caching the inverse of a matrix
 
-## Write a short comment describing this function
+## This function creates a special "matrix" object that can cache its inverse.
+## Below are two functions.
 
-makeCacheMatrix <- function(x = matrix()) {
+## makeCacheMatrix is used to create a special object that stores a matrix 
+## and cache's its inverse.
+
+## The cacheSolve function computes the inverse of the special "matrix" 
+## returned by makeCacheMatrix above. 
+## If the inverse has already been calculated (and the matrix has not changed), 
+## then the cachesolve should retrieve the inverse from the cache.
 
-}
 
+makeCacheMatrix <- function(x = matrix()) {
+  m <- NULL
+      #The set function sets the value of the matrix
+      set <- function(k) {
+        x <<- k
+        m <<- NULL
+      }
+    #The get function gets the value of the vector
+    get <- function() x
+    #Solve the inverse matrix of x
+    setinverse <- function(solve) m <<- solve
+    #Get the list of matrix in a list
+    getinverse <- function() m
+    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'
-}
+    m <- x$getinverse()
+    if(!is.null(m)) {
+      message("getting cached data")
+      return(m)
+    }
+    data <- x$get()
+    m <- solve(data,...)
+    x$setinverse(m)
+    m
+  }
+
+## Test this function.
+## Step 1. define a matrix
+mm=matrix(c(1,2,3,1), nrow=2,ncol=2)
+## Step 2. define a specific matrix x that contains the output from
+x <- makeCacheMatrix(mm)
+## Step 3. For debug reason, check whether the determinant det(mm) is zero or not
+det(mm)
+## This should generate the first-time output
+cacheSolve(x)
+## This should return the generated value in the previous command
+cacheSolve(x)
