cachematrix.R

## These two functions can be used to compute and cache the inverse 
## of one matrix so that it won't be computed repeatedly if it has
## been computed and cached before. 
##

## makeChacheMatrix function creates a special "matrix" object that 
## can cache its inverse. 
##

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


## cacheSolve 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.
##

cacheSolve <- function(x, ...) {
    ## Return a matrix that is the inverse of 'x'
    inv <- x$getinverse()
    if(!is.null(inv)) {
        message("getting cached data")
        return(inv)
    }
    data <- x$get()
    inv <- solve(data, ...)
    x$setinverse(inv)
    inv
}