Implement makeCacheMatrix and cacheSolve

hisashim · hisashim · commit 464773d1f69b · 2014-09-21T19:57:51.000+09:00
diff --git a/cachematrix.R b/cachematrix.R
@@ -1,15 +1,41 @@
-## Put comments here that give an overall description of what your
-## functions do
+## makeCacheMatrix: This function creates a special "matrix" object that
+## can cache its inverse.
+##
+## cacheSolve: This 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.
 
-## Write a short comment describing this function
+## makeCacheMatrix creates a special "matrix", which is really a list
+## containing functions to get/set the matrix and its inverse
 
 makeCacheMatrix <- function(x = matrix()) {
-
+        i <- NULL
+        set <- function(y) {
+                x <<- y
+                i <<- NULL
+        }
+        get <- function() x
+        setinverse <- function(inverse) i <<- inverse
+        getinverse <- function() i
+        list(set = set, get = get,
+             setinverse = setinverse,
+             getinverse = getinverse)
 }
 
 
-## Write a short comment describing this function
+## cacheSolve returns an inverse of the given matrix, utilising cache
+## mechanism provided by makeCacheMatrix
 
 cacheSolve <- function(x, ...) {
         ## Return a matrix that is the inverse of 'x'
+        i <- x$getinverse()
+        if(!is.null(i)) {
+                message("getting cached data")
+                return(i)
+        }
+        data <- x$get()
+        i <- solve(data, ...)
+        x$setinverse(i)
+        i
 }
