Creation of...

Richard Shaw · Richard Shaw · commit a32e4a381a66 · 2014-06-20T16:09:58.000-04:00
makeCacheMatrix: This function creates a special "matrix" object that can cache its inverse.
cacheSolve: This function computes the inverse of the special "matrix" returned by makeCacheMatrix above.
diff --git a/cachematrix.R b/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 creates a special "matrix", which is really a list containing a function which
+## 0. Checks we have a square matrix
+## 1. set the value of the matrix
+## 2. get the value of the matrix
+## 3. set the value of the matrix inverse
+## 4. get the value of the matrix inverse
 makeCacheMatrix <- function(x = matrix()) {
-
+  
+  ## Validation you can only inverse a square matrix using solve()
+  ## Check we have a square matrix
+  if(nrow(x) != ncol(x)) {
+    stop('Matrix isn\'t square. Inverse can only be calculated on square matrix')
+  }
+  
+  #On creation initalize value of inverse var
+  i <- NULL
+  ## Save matrix data in object
+  ## Clears any previously calculated inverse
+  set <- function(y) {
+    x <<- y
+    i <<- NULL 
+  }
+  ## Returns cached matrix data
+  get <- function() x
+  ## Cache inverse of matrix
+  setInverse <- function(inverse) i <<- inverse
+  ## Return cache inverse of matrix
+  getInverse <- function() i
+  
+  list(set = set, get = get,
+       setInverse = setInverse,
+       getInverse = getInverse)
+  
 }
 
-
-## Write a short comment describing this function
-
+## Function calculates the inverse of the special "matrix" created with the makeCacheMatrix function. 
+## 'x' is a makeCacheMatrix object
+## It first checks to see if the inverse has already been calculated. 
+## If it has gets it the inverse from the cache and skips the computation. 
+## Otherwise, it calculates the inverse of 'x' 
+## and sets the value of the inverse matrix in the cache using the setinverse function.
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  ## Looks for inverse in cache
+  i <- x$getInverse()
+  if(!is.null(i)) {
+    message("getting cached data")
+    ## Inverse is not null so return value
+    return(i)
+  }
+  ## Inverse is not availble so calculate
+  ## Get matrix data from the makeCacheMatrix object
+  data <- x$get()
+  ## Calculate inverse of data
+  i <- solve(data, ...)
+  ## Cache inverse in object
+  x$setInverse(i)
+  ## Return inverse of matrix
+  i
 }
