Complete assignment 2

Author: tjad

cachematrix.R

@@ -1,15 +1,62 @@
 ## Put comments here that give an overall description of what your
 ## functions do
 
-## Write a short comment describing this function
-
-makeCacheMatrix <- function(x = matrix()) {
+# Special function to make an 'object' that will hold a matrix and a cached version of its inverse
+makeCacheMatrix <- function(m = matrix()){
+  matrix <- m
+  cached_inverse <- NULL
+  
+  changed <- FALSE # Invariant approach to help with performance -so that the solveCache function doesn't have to track a copy of the matrix to know whether it has changed
+                   # This is fine in  this scenario as there is only one function defining what the "changed" status means.
+  
+  #Set the matrix that this functions wraps
+  set <- function(m) {
+    if(!identical(matrix, m)) changed <<- TRUE
+    matrix <<- m
+  }
+  
+  #get the matrix that this function wraps
+  get <- function() matrix
+  
+  #setter for cached inverse
+  set_cached_inverse <- function(cache){
+    changed <<- FALSE
+    cached_inverse <<- cache
+    cached_inverse
+  }
+  #getter for cached inverse
+  get_cached_inverse <- function(){
+    cached_inverse
+  } 
+  
+  #function to get changed status
+  has_changed <- function() changed
+    
+  #function mapping
+  list(set = set, get = get,
+       set_cached_inverse = set_cached_inverse,
+       get_cached_inverse = get_cached_inverse,
+       has_changed = has_changed)
+  
+} 
 
+# Function that takes in a CacheMatrix and if not already calculated, calculates the matrix's inverse 
+# and updating the CacheMatrix to store the new value 
+cacheSolve <- function(cached_matrix, ...) {
+  
+  ## Return a matrix that is the inverse of 'cached_matrix'
+  inverse <- cached_matrix$get_cached_inverse()
+  
+  #Only caclulate inverse if matrix has changed or it hasn't been calculated yet
+  if(cached_matrix$has_changed() | 
+       is.null(cached_matrix$get_cached_inverse())){
+    message("Recalculating inverse")
+    #calculate and set inverse
+    return(cached_matrix$set_cached_inverse( 
+                              solve(cached_matrix$get())
+                              ))
+  
+  }
+  inverse
 }
 
-
-## Write a short comment describing this function
-
-cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
-}