assigment completed

Author: Tadas Sugintas

cachematrix.R

@@ -1,15 +1,60 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Solution to Programming Assigment 2
+## creates 2 functions - 
+## one for creating a special type of object that can cache the matrix inverse; 
+## another for checking if the inverse is already in the cache and returing it if so. Otherwise it calculates the inverse and caches it
 
-## Write a short comment describing this function
+## Usage demonstration:
+## create a matrix that we will use for testing:
+## m1 <- matrix(c(4,5,6,3,4,5,11,44,66), 3,3)
 
-makeCacheMatrix <- function(x = matrix()) {
+## create a special object that holds the matrix and its inverse. There is no inverse yet:
+## ca1 <- makeCacheMatrix(m1)
+## get the matrix inverse. There is no pre-cached inverse, so it has to be calculated:
+## u <- cacheSolve(ca1)
+## print the inverse:
+## u
+##             [,1]        [,2]        [,3]
+## [1,] -4.00000000  13.0000000 -8.00000000
+## [2,]  6.00000000 -18.0000000 11.00000000
+## [3,] -0.09090909   0.1818182 -0.09090909
+##
+## get the matrix inverse again. This time is it retrieved from cache and a message is displayed:
+## w <- cacheSolve(ca1)
+## we have cached matrix, returning
+##
+## print the inverse to verify that it is the same
+## w
 
+## Creates an object that can hold a matrix and its inverse
+makeCacheMatrix <- function(x = matrix()) {
+    i <- NULL
+    getMatrix <- function() x
+    setMatrix <- function(y) {
+      x <<- y
+      i <<- NULL
+    }
+    getInverse <- function() i
+    setInverse <- function(inverse) {
+      i <<- inverse
+    } 
+    list(getMatrix = getMatrix, setMatrix = setMatrix, getInverse = getInverse, setInverse = setInverse)
 }
 
 
-## Write a short comment describing this function
-
+## Accepts special object that holds a matrix and its inverse 
+## returns an inverse from the cache if there is one. Otherwise calculates the inverse, caches it returns it. 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+        i <- x$getInverse()
+        if (!is.null(i)) {
+          message("we have cached matrix, returning it")
+          return(i)
+        }
+        ## there is no inverse calculated for this matrix yet.
+        ## getting the matrix from the special object:
+        matrix <- x$getMatrix()
+        ## calculating the inverse
+        inverse <- solve(matrix)
+        ## caching in the special object that is held in the parent environment
+        x$setInverse(inverse)
+        inverse
 }