added makeCacheMatrix and cacheSolve functions

Author: dshupp

cachematrix.R

@@ -2,14 +2,54 @@
 ## functions do
 
 ## Write a short comment describing this function
-
-makeCacheMatrix <- function(x = matrix()) {
+# creates a list to encapsulate a matrix with various helper functions for that matrix, particularly a caching mechanism
+# logic for the caching is not included here, this function only creates the data structure that will be used by separate
+# caching logic. 
+# helper functions include: 
+# getInverse: returns the matrix inverse (computation is cached automatically, no need to set the value manually...)
+# get and set: getting and setting the matrix object (setting clears the cached inverse)
+# makeCacheMatrix ssumes the matrix is always invertible
+makeCacheMatrix <- function(subjectMatrix = matrix()) {
+  inverse <- NULL
+  set <- function(newMatrix) {
+    subjectMatrix <<- newMatrix
+    inverse <<- NULL
+  }
+  
+  get <- function() {
+    subjectMatrix
+  }
+  
+  getInverse <- function() {
+    inverse
+  }
+  
+  setInverse <- function(newInverse) {
+    inverse <<- newInverse
+  }
+  
+  # assign a reference to the function to the label of the same name
+  list(set = set, get = get, getInverse = getInverse, setInverse = setInverse)
 
 }
 
 
 ## Write a short comment describing this function
-
+# a caching wrapper for the solve() command when being used to calculate the matrix inverse. 
+# to be used in conjunction with makeCacheMatrix, expects a data structure defined by makeCacheMatrix()
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  ## Return a matrix that is the inverse of 'x'
+    
+  if (is.null(x$getInverse())) {
+    # compute and cache the matrix inverse
+    message("cachematrix: cache empty, calculating inverse with solve()")
+    x$setInverse(solve(x$get(), ...))    
+  } else {
+    #report that we're using a cached value
+    message("cachematrix: using cached value")
+  }
+  
+  # return the cached inverse
+  x$getInverse()
+  
 }