cachematrix.R

## Coursera - R Programming
## Programming assignment #2
##
## Matrix inversion is usually a costly computation and there may be some 
## benefit to caching the inverse rather than compute it repeatedly.
## This file contains 2 functions that cache the inverse of a matrix.


## This function creates a special "matrix" object that can cache its inverse.
## It really is a list containing a function to
##   1) set the value of the matrix
##   2) get the value of the matrix
##   3) set the value of the inverse
##   4) get the value of the inverse

makeCacheMatrix <- function(x = matrix()) {
     i <- NULL
     set <- function(y) {
          x <<- y
          i <<- NULL
     }
     get <- function() x
     setinverse <- function(inverse) i <<- inverse
     getinverse <- function() i
     list(set = set, get = get,
          setinverse = setinverse,
          getinverse = getinverse)
}


## This function computes the inverse of the special "matrix" returned by 
## makeCacheMatrix above. If the inverse has already been calculated (and 
## the matrix has not changed), then the cachesolve should retrieve the 
## inverse from the cache.
##
## It returns a matrix that is the inverse of 'x'

cacheSolve <- function(x, ...) {
     i <- x$getinverse()
     if(!is.null(i)) {
          message("getting cached data")
          return(i)
     }
     data <- x$get()
     i <- solve(data, ...)
     x$setinverse(i)
     i
}