both functions

Author: bobuva

cachematrix.R

@@ -1,15 +1,51 @@
 ## Put comments here that give an overall description of what your
 ## functions do
 
-## Write a short comment describing this function
+## Creates a special type of matrix object, called a CacheMatrix, 
+## which can cache its inverse matrix.
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  cacheMatrix <- NULL
+  inverseMatrix <- NULL
+  
+  set <- function(aMatrix) {
+    cacheMatrix <<- aMatrix
+    inverseMatrix <<- NULL
+  }
+  
+  get <- function() x
+  
+  setInverse <- function(inverse) inverseMatrix <<- inverse
+  
+  getInverse <- function() inverseMatrix
+  
+  list(set = set, get = get,
+       setInverse = setInverse,
+       getInverse = getInverse)
+  
 }
 
 
-## Write a short comment describing this function
-
+## Computes the inverse of a CacheMatrix, which is a matrix returned by makeCacheMatrix.
+## If the matrix has not changed since the last call to cacheSolve, a cached copy of
+## the inverse matrix will be returned, otherwise the inverse is computed, cached
+## and returned.
+##
+## PreCondition: The matrix, x, is invertible
 cacheSolve <- function(x, ...) {
         ## Return a matrix that is the inverse of 'x'
+
+  inv <- x$getInverse()
+  if (!is.null(inv)) {
+    message("getting cached data")
+    return(inv)
+  }
+  
+  # get the inverse
+  data <- x$get()
+  inv <- solve(data)
+  
+  x$setInverse(inv)  # cache inv
+  
+  inv  # returns inv
 }