cachematrix.R

  ## This function takes a square matrix as its argument and creates a special matrix
  ## object (a list of 4 functions) storing this matrix.
  ##
  ## Examples:
  ## The following creates a 3 by 3 matrix containing random values:
  ## matrix.object <- makeCacheMatrix(matrix(nrow = 3, ncol = 3, rnorm(9)))
  ##
  ## This prints the matrix:
  ## matrix.object$get()
  
makeCacheMatrix <- function(x = matrix()) {
    i <- NULL
    set <- function(y) {
        x <<- y
        i <<- NULL
        list(set = set, get = get)
    }
    get <- function() x
    setinv <- function(inverse) i <<- inverse
    getinv <- function() i
    list(set = set, get = get,
       setinv = setinv,
       getinv = getinv)
}



  ## This function calculates and stores the cached inverse matrix of a special matrix 
  ## object, if it has not been stored yet, and the returns it.
  ## If there already exists a cached value, returns it without calculating it again.
  ##
  ## Use: cacheSolve(matrix.object)
  
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
}