cachematrix.R

## Matrix inversion is usually a costly computation and their may be some 
## benefit to caching the inverse of a matrix rather than compute it repeatedly.
## The following functions allow to do that.
## Note, the function assumes that the matrix supplied is square and always invertible.

## This function creates a special "matrix" object that can cache its inverse.
## Innput should be a square matrix (invertible)

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



## 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.

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