From 7b8c1ec99090dbd99a07d23e44a780079a51c946 Mon Sep 17 00:00:00 2001
From: Jerome Jia <iusr@me.com>
Date: Mon, 22 Dec 2014 02:29:37 +0800
Subject: [PATCH] submission for peer assessment

---
 .gitignore    |  3 +++
 cachematrix.R | 37 +++++++++++++++++++++++++++++++------
 2 files changed, 34 insertions(+), 6 deletions(-)
 create mode 100644 .gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000000..807ea251739
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+.Rproj.user
+.Rhistory
+.RData
diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..cb8d9b2a6e7 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,40 @@
-## Put comments here that give an overall description of what your
-## functions do
+## A set of functions that aids frequent access of results of matrix inversion operations,
+## best fit for matrices with large dimensions.
 
-## Write a short comment describing this function
+## Function to create a special matrix whose inversion is cached for subsequent access
 
 makeCacheMatrix <- function(x = matrix()) {
-
+    i <- NULL
+    set <- function(y) {
+        x <<- y
+        i <<- NULL
+    }
+    get <- function() x
+    setinv <- function(inv) i <<- inv
+    getinv <- function() i
+    list(set = set, get = get,
+         setinv = setinv,
+         getinv = getinv)
 }
 
 
-## Write a short comment describing this function
+## Function to retrieve the inversion of any matrix created via makeCacheMatrix if already
+## cached, otherwise calculcates the inversion and cache it for the matrix
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    ## returns NA if x is not properly created via makeCacheMatrix
+    if(!"getinv" %in% names(x) | !"setinv" %in% names(x)) {
+        warning("input matrix not wrapped by makeCacheMatrix")
+        return(NA)
+    }
+    ## Return a matrix that is the inverse of 'x'
+    i <- x$getinv()
+    if(!is.null(i)) {
+        message("getting cached data")
+        return(i)
+    }
+    data <- x$get()
+    i <- solve(data, ...) %*% data
+    x$setinv(i)
+    i
 }