Adding solution for the programming assignment

Author: nirvanka

cachematrix.R

@@ -1,15 +1,46 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Matrix inversion is usually a costly computation and there may be some benefit to caching the inverse of a matrix rather than computing it repeatedly
 
-## Write a short comment describing this function
+## This function creates a special "matrix" object that can cache its inverse.
 
 makeCacheMatrix <- function(x = matrix()) {
-
+    m <- NULL
+    set <- function(y) {
+        x <<- y
+        m <<- NULL
+    }
+    get <- function() x
+    setinverse <- function(inverse) m <<- inverse
+    getinverse <- function() m
+    list(set = set, get = get,
+         setinverse = setinverse,
+         getinverse = getinverse)
 }
 
 
-## Write a short comment describing this function
+## 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 is a bit dumb cache, as it doesn't take into consideration that '...' arguments that might have changed in the second call
+### and returns the first value, even though calling solve with extra arguments would error
+### e.g. solve(my_matrix, mean)
+### 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.
+### whereas:
+### cached = makeCacheMatrix(my_matrix)
+### cacheSolve(cached) gives an inverse
+### cacheSolve(cached, mean) second call gives the same result even though it should normally error
+### The solution would be to either hash all arguments or store them in a list that would be a key for getting cached martices,
+### but that is beyond this programming assignment.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    ## Return a matrix that is the inverse of 'x'
+    m <- x$getinverse()
+    if(!is.null(m)) {
+        message("getting cached data")
+        return(m)
+    }
+    data <- x$get()
+    m <- solve(data, ...)
+    x$setinverse(m)
+    m
 }