cachematrix.R

# This function creates a special "matrix" object that can cache its inverse.

# 1. set the value of the matrix
# 2. get the value of the matrix
# 3. set the value of inverse of the matrix
# 4. get the value of inverse of the matrix

makeCacheMatrix <- function(x = matrix()) {
  inv <- NULL
  setmatrix <- function(y) {
    x <<- y
    inv <<- NULL
  }
  getmatrix <- function() x
  setinverse <- function(inverse) inv <<- inverse
  getinverse <- function() inv
  list(setmatrix=setmatrix, getmatrix=getmatrix, setinverse=setinverse, getinverse=getinverse)
}




# 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.



# This function assumes that the matrix is always invertible.
 cacheSolve <- function(x, ...) {
     inv <- x$getinverse()
     if(!is.null(inv)) {
         message("getting cached data.")
         return(inv)
     }
     data <- x$getmatrix()
     inv <- solve(data)
     x$setinverse(inv)
     inv
 }

## Sample run:

# my_matrix <- makeCacheMatrix(matrix(1:4, 2, 2))


#> my_matrix$getmatrix()
#     [,1] [,2]
#[1,]    1    3
#[2,]    2    4

#> cacheSolve(my_matrix)
#     [,1] [,2]
#[1,]   -2  1.5
#[2,]    1 -0.5
#>