From dd8abd394714c6344f64702fb3d73658fe9e16e4 Mon Sep 17 00:00:00 2001
From: Stephen Abrams <abrams.stephen@gmail.com>
Date: Sun, 21 Feb 2016 21:42:54 -0500
Subject: [PATCH 1/3] Completes assignment 2

---
 cachematrix.R | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..a320a616e76 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,37 @@
 ## Put comments here that give an overall description of what your
 ## functions do
 
-## Write a short comment describing this function
-
+##  returns a list of functions to get/set an 'internal' matrix and get/set its inverse. 
+## (get, set, getinv, setinv).
+## If the matrix is 'set' via this list's set function, the inverse matrix will be cleared.
 makeCacheMatrix <- function(x = matrix()) {
+  m <- NULL
+  set <- function(y) {
+    x <<- y
+    m <<- NULL
+  }
+  get <- function() x
+  setinv <- function(matinv) m <<- matinv
+  getinv <- function() m
+  list(set = set, get = get,
+       setinv = setinv,
+       getinv = getinv)
 
 }
 
 
-## Write a short comment describing this function
-
+## Returns inverse of x, storing the computation of the inverse
+## x is not actually a matrix, but rather a list generated by makeCacheMatrix
 cacheSolve <- function(x, ...) {
+  
+  m <- x$getinv()
+  if(!is.null(m)) {
+    message("getting cached data")
+    return(m)
+  }
+  data <- x$get()
+  m <- matrix(rev(c(data)), nrow=nrow(data), ncol=ncol(data))
+  x$setinv(m)
+  m
         ## Return a matrix that is the inverse of 'x'
 }

From 8d3d468b791d7477cdee450d95637a94dd48361d Mon Sep 17 00:00:00 2001
From: Stephen Abrams <abrams.stephen@gmail.com>
Date: Sun, 21 Feb 2016 21:50:02 -0500
Subject: [PATCH 2/3] add additional comments and include helper test script
 whose contents I used on console to verify

---
 cachematrix.R |  3 +++
 test.R        | 10 ++++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 test.R

diff --git a/cachematrix.R b/cachematrix.R
index a320a616e76..2f747dc7362 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -22,6 +22,9 @@ makeCacheMatrix <- function(x = matrix()) {
 
 ## Returns inverse of x, storing the computation of the inverse
 ## x is not actually a matrix, but rather a list generated by makeCacheMatrix
+## This will set the 'internal' inverse matrix for mackCacheMatrix context if
+## it doesn't already exist, and will simply return that matrix if it exists w/o
+## recomputing.
 cacheSolve <- function(x, ...) {
   
   m <- x$getinv()
diff --git a/test.R b/test.R
new file mode 100644
index 00000000000..7195dbb6fdb
--- /dev/null
+++ b/test.R
@@ -0,0 +1,10 @@
+source('./cachematrix.R')
+x <- matrix(1:20,  nrow=3, ncol=2)
+y <- matrix(100:106,  nrow=3, ncol=2)
+z <- matrix(c("a", "v", "b", "aa", "ab", "cc"),  nrow=3, ncol=3)
+cmx <- makeCacheMatrix(x)
+cmy <- makeCacheMatrix(y)
+cmz <- makeCacheMatrix(z)
+invx <- cacheSolve(cmx)
+invy <- cacheSolve(cmy)
+invz <- cacheSolve(cmz)
\ No newline at end of file

From 244ef491e4c00d1ea6cc7efbf472b3c4613b7195 Mon Sep 17 00:00:00 2001
From: Stephen Abrams <abrams.stephen@gmail.com>
Date: Sun, 21 Feb 2016 22:38:00 -0500
Subject: [PATCH 3/3] fix after learning to get inverse by calling solve

---
 cachematrix.R |  2 +-
 test.R        | 11 ++++++-----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index 2f747dc7362..1174ca5054b 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -33,7 +33,7 @@ cacheSolve <- function(x, ...) {
     return(m)
   }
   data <- x$get()
-  m <- matrix(rev(c(data)), nrow=nrow(data), ncol=ncol(data))
+  m <- solve(data)
   x$setinv(m)
   m
         ## Return a matrix that is the inverse of 'x'
diff --git a/test.R b/test.R
index 7195dbb6fdb..8c1d7442748 100644
--- a/test.R
+++ b/test.R
@@ -1,10 +1,11 @@
 source('./cachematrix.R')
-x <- matrix(1:20,  nrow=3, ncol=2)
-y <- matrix(100:106,  nrow=3, ncol=2)
-z <- matrix(c("a", "v", "b", "aa", "ab", "cc"),  nrow=3, ncol=3)
+x <- matrix(c(2,2,3,2),  nrow=2, ncol=2)
+y <- matrix(c(1, -1, 1, 2),  nrow=2, ncol=2)
 cmx <- makeCacheMatrix(x)
 cmy <- makeCacheMatrix(y)
-cmz <- makeCacheMatrix(z)
 invx <- cacheSolve(cmx)
 invy <- cacheSolve(cmy)
-invz <- cacheSolve(cmz)
\ No newline at end of file
+solve(cacheSolve(cmy))
+solve(cacheSolve(cmx))
+solve(cacheSolve(cmy))
+solve(cacheSolve(cmx))