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 pair of functions cache the inverse of a matrix.
## functions do

## This function creates a special matrix object which is actually 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 of the matrix
## 4. get the value of the inverse of the matrix

makeCacheMatrix <- function(x = matrix()) {
        i <- NULL
        set <- function(y) {
                x <<- y
                i <<- NULL
        }
        get <- function() x
        setinv <- function(inv) i <<- inv
        getinv <- function() i
        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 cacheSolve should retrieve the inverse from 
## the cache. Otherwise, it computes the inverse and sets the value in the 
## cache via setinverse function.

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