cachematrix.R

## Put comments here that give an overall description of what your
## functions do

## This function creates a list. `set` stores the matrix. `get` retrieves the matrix.
## `setinv` caches the inverse. `getinv` returns the inverse.
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)
}


## This function firsts looks for a cached inverse. If it is not cached the
## inverse is calculated and then cached. The function returns the inverse. 
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
}