initial version

Author: egarson

cachematrix.R

@@ -1,15 +1,50 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
+## Coursera "R Programming", Assignment 2.
+##
+## Author: Edward Garson
+## Date: December 2014
+##
+## https://class.coursera.org/rprog-016/human_grading/view/courses/972581/assessments/3/submissions
 
+## Return a list object that encapsulates a given matrix and its calculated inverse.
+## `x_inv' is the memoized variable that caches the inverse
+## `inverse' is an accessor function for the inverse of the given matrix (`x_inv')
+## `cache' is a function to set the value of `x_inv', and conveniently returns it
 makeCacheMatrix <- function(x = matrix()) {
-
+    x_inv <- NULL
+    inverse <- function() x_inv
+    cache <- function(inv) { x_inv <<- inv; x_inv }
+    list(matrix = x, inverse = inverse, cache = cache)
 }
 
+## Returns the inverse of `x$matrix', potentially retrieving it from cache
+cacheSolve <- function(x, ...) {
+    if (!is.null(x$inverse())) {
+        # message("cache hit")
+        return(x$inverse())
+    }
+    x$cache(solve(x$matrix, ...)) # n.b. this *returns* the inverse in addition to caching it
+}
 
-## Write a short comment describing this function
+makeVector <- function(x = numeric()) {
+    m <- NULL
+    set <- function(y) {
+        x <<- y
+        m <<- NULL
+    }
+    get <- function() x
+    setmean <- function(mean) m <<- mean
+    getmean <- function() m
+    list(set = set, get = get, setmean = setmean, getmean = getmean)
+}
 
-cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+cachemean <- function(x, ...) {
+    m <- x$getmean()
+    if(!is.null(m)) {
+        message("getting cached data")
+        return(m)
+    }
+    data <- x$get()
+    m <- mean(data, ...)
+    x$setmean(m)
+    m
 }