cachematrix.R

## Our aim in this experiment is to write a pair of functions, namely, 
## "makeCacheMatrix" and "cacheSolve" that cache the inverse of a matrix

## makeCacheMatrix is a function which creates a special "matrix" object that can 
## cache its inverse for the input (which is an invertible square matrix)

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


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

## ---------------Checking the program------------------------
## m <- matrix(rnorm(16),4,4)
## m1 <- makeCacheMatrix(m)
## cacheSolve(m1)

## [,1]       [,2]       [,3]       [,4]
## [1,] -0.1653269  0.2592203  0.6176218 -0.7520955
## [2,]  0.2828334 -0.1853499  0.4511382  0.2094365
## [3,]  0.1434840  1.0413868 -0.3550853 -0.3261154
## [4,]  0.1793583 -0.4252171 -0.4371493 -0.1749830