cachematrix.R

##This script contains two functions that can be used to cache the inverse of a
##matrix making use of the scoping assignment "<<-". The matrix is assumed to 
##be invertible.

##The makeCacheMatrix function creates a special "matrix" object that can
##cache its inverse. It 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 inverse of the matrix
## 4- get the value of inverse of the matrix

makeCacheMatrix <- function(x = matrix()) {
    inv <- NULL
    set <- function(y) {
        x <<- y
        inv <<- NULL
    }
    get <- function() x
    setinv <- function(solve) inv <<- solve
    getinv <- function() inv
    list(set = set, get = get,
         setinv = setinv,
         getinv = getinv)
}


##The cacheSolve function returns the inverse of the special "matrix"
##created with the makeCacheMatrix function. It first checks if the
##inverse has already been computed. If so, it gets the result from 
##the cache and skips the computation. If not it calculates the inverse and
##sets the value in the cache through the setinv function.

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