rdpeng · Mar 26, 2016 · Mar 26, 2016 · Mar 26, 2016 · Mar 26, 2016
Showing with 40 additions and 6 deletions.

+40 −6 cachematrix.R
diff --git a/cachematrix.R b/cachematrix.R
@@ -1,15 +1,49 @@
-## Put comments here that give an overall description of what your
-## functions do
+## makeCacheMatrix() creates a special "matrix" object that
+## can cache its inverse.
+## cacheSolve() returns the inverse of such a special "matrix".
 
-## Write a short comment describing this function
 
+## Creates a "matrix" that can cache its own inverse.
+## Returns a list containing functions to view or edit the matrix and its
+## inverse.
 makeCacheMatrix <- function(x = matrix()) {
 
+        ## Inverse not yet computed
+        inv <- NULL
+        ## The setter function of the matrix
+        set <- function( y ) {
+                x <<- y
+                ## The matrix just got a new value, so
+                ## the inverse is not yet known
+                inv <<- NULL
+        }
+        ## The getter function of the matrix
+        get <- function() x
+        ## The setter function of the inverse of the matrix
+        setinv <- function( invv ) inv <<- invv
+        ## The getter function of the inverse of the matrix
+        getinv <- function() inv
+        ## Return the list that makes the matrix functions accessible
+        list( set = set, get = get,
+              setinv = setinv,
+              getinv = getinv )
 }
 
 
-## Write a short comment describing this function
-
+## Returns the inverse of the special matrix 'x', either from
+## cache (if available), or by computing it.
+## ASSUME that the matrix supplied is always invertible.
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+
+        ## Get the stored inverse (if any) from 'x'
+        inv <- x$getinv()
+        ## If the inverse is cached, return cached value
+        if ( !is.null(inv) ) {
+                message("Getting cached data...")
+                return( inv )
+        } ## Else get the data...
+        data <- x$get()
+        inv <- solve( data, ... ) ## ... compute its inverse ...
+        x$setinv( inv )           ## ... set the inverse in x's cache, and...
+        inv                       ## ... return the computed inverse.
 }