cachematrix.R

## to cache up internal state of a matrix in order to save time taken
## on recomputation

## to create a special 'matrix' which is able to cache inverse matrix

makeCacheMatrix <- function( x = matrix() ) {
        ## inverse matrix cache, initially set to NULL
        im <- NULL
        ## set the value of the matrix
        set <- function( y ) {
                x <<- y
                im <<- NULL
        }
        ## get the vlaue of the matrix
        get <- function() {
                x
        }
        ## set the value of the inverse matrix
        setInverse <- function( m ) {
                im <<- m
        }
        ## set the value of the inverse matrix
        getInverse <- function() {
                im
        }
        list( set = set,
                get = get,
                setInverse = setInverse,
                getInverse = getInverse )
}


## to calculate the inverse matrix of the special 'matrix' created
## with makeCacheMatrix

cacheSolve <- function( x, ... ) {
        ## retrieve internally cached inverse matrix
        im <- x$getInverse()
        ## if the cached inverse matrix is not null, use it as the
        ## result of this function
        if( ! is.null( im ) ) {
                message( "getting cached data" )
                return( im )
        }
        ## otherwise, compute the inverse matirx in the original way
        data <- x$get()
        im <- solve( data, ... )
        ## store the inverse matrix in the cache
        x$setInverse( im )
        ## return the inverse matrix
        im
}