R Programming Assignment 2

This is the second R Programming assignment.
leophill · Jun 17, 2014 · ebb2a99 · ebb2a99
1 parent 7f657dd
commit ebb2a99
Showing 1 changed file with 51 additions and 6 deletions.
diff --git a/cachematrix.R b/cachematrix.R
@@ -1,15 +1,60 @@
-## Put comments here that give an overall description of what your
-## functions do
+## The code caches the Inverse of a Matrix (which is assumed to be invertible) to help avoid
+## the costly operation of computing the Inverse each time, especially if it was calculated
+## during a previous run.
+## A typical call to get or set the cached Inverse of Matrix MX is : cacheSolve(makeCacheMatrix(MX))
 
-## Write a short comment describing this function
+## makeCacheMatrix creates a special "Matrix", which is a list containing four main functions to
+## get or set the value of the Matrix, to get or set the value of the Inverse Matrix, respectively.
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  ## Initialize "inv" Matrix to null
+  inv <- NULL
+
+  ## Function to set the value of Matrix "x" to that of Matrix "y".
+  set <- function(y) {
+    x <<- y
+    inv <<- NULL
+  }
+
+  ## Function to get the value of Matrix "x"
+  get <- function() x
+
+  ## Function to assign the value of the inverse Matrix to Matrix "inv"
+  setinv <- function(inverse) inv <<- inverse
+
+  ## Function to get the cached value of Matrix "inv"
+  getinv <- function() inv
+
+  ## Build a list of all four functions above
+  list(set = set, get = get,
+       setinv = setinv,
+       getinv = getinv)
 }
 
 
-## Write a short comment describing this function
+## cacheSolve first checks to see if an Inverse Matrix has already been calculated for the special
+## Matrix returned by makeCacheMatrix function above. If so, then it retrieves the cached value.
+## If not, it calculates the Inverse Matrix of the special Matrix using the "solve" function.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  ## Return a Matrix that is the Inverse of 'x'
+
+  ## Get cached value for the Inverse of Matrix "x" if any
+  inv <- x$getinv()
+
+  ## Check and return the cached value if the Inverse of "x" already exists in the cache 
+  if(!is.null(inv)) {
+    message("getting cached data")
+    return(inv)
+  }
+
+  ## No cached data. Save and find the inverse of Matrix "x" using "solve" function
+  data <- x$get()
+  inv <- solve(data, ...)
+
+  ## Store newly computed value into the cache
+  x$setinv(inv)
+
+  ## Return the value of the Inverse of Matrix "x"
+  inv
 }