Implement a matrix with a cached inverse

RKushnir · RKushnir · commit a0749d233129 · 2015-02-15T22:28:48.000+02:00
diff --git a/cachematrix.R b/cachematrix.R
@@ -1,15 +1,42 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Matrix inversion is usually a costly computation,
+## so there may be some benefit to caching the inverse of a matrix
+## rather than computing it repeatedly.
+## The following functions implement the matrix inverse caching mechanism
 
-## Write a short comment describing this function
+## This function creates a special "matrix" object that can cache its inverse
 
 makeCacheMatrix <- function(x = matrix()) {
+  inverse <- NULL
 
+  set <- function(y) {
+    x <<- y
+    inverse <<- NULL
+  }
+  get <- function() x
+  setinverse <- function(i) inverse <<- i
+  getinverse <- function() inverse
+
+  list(set = set, get = get,
+    setinverse = setinverse,
+    getinverse = getinverse)
 }
 
 
-## Write a short comment describing this function
+## 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 cacheSolve retrieves the inverse from the cache
 
 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
 }
