Update cachematrix.R

cachematrix.R

@@ -1,15 +1,40 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
+## makeCacheMatrix and cacheSolve functions combined provide a 
+## feature to create square invertible matrix that caches its inverse 
+## for time efficient repeated invocation of solve()
 
+## makeCacheMatrix creates a special matrix that  
+## stores the matrix along with its inverse and provides
+## getters and setters to access those.
+## The inverse is set to NULL during the construction for efficiency.
 makeCacheMatrix <- function(x = matrix()) {
-
+        inv <- NULL
+        set <- function(y) {
+                x <<- y
+                inv <<- NULL
+        }
+
+        get <- function() x
+        setinv <- function(m.inv) inv <<- m.inv
+        getinv <- function() inv
+        list(set = set, get = get,
+             setinv = setinv,
+             getinv = getinv)
 }
 
 
-## Write a short comment describing this function
-
+## calculates the inverse of a matrix
+## Assumes that x is an invertible square matrix
+## First invocation caches the inverse returned by the solve(...) and the
+## subsequent call returns it straight from the cache
 cacheSolve <- function(x, ...) {
         ## Return a matrix that is the inverse of 'x'
+        m <- x$getinv()
+        if(!is.null(m)) {
+                message("getting cached data")
+                return(m)
+        }
+        data <- x$get()
+        m <- solve(data, ...)
+        x$setinv(m)
+        m
 }