From 44dd7aa7db73df79ba760beb5343cae5b18304f7 Mon Sep 17 00:00:00 2001
From: Miguel Rocha <mrocha@di.uminho.pt>
Date: Mon, 21 Apr 2014 18:29:25 +0100
Subject: [PATCH 1/2] solved the assignment

---
 cachematrix.R | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..810872a0c73 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,41 @@
 ## Put comments here that give an overall description of what your
 ## functions do
 
-## Write a short comment describing this function
+## This function creates a list with functions to create the cached matrix and its inverse
+## each field contains a function: set (sets the matrix), get (returns the matrix), 
+## setinv (sets the inverse), getinv (returns the inverse)
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  inv = NULL
+  set = function(mat)
+  {
+    m <<- mat
+    inv <<- NULL
+  }
+  get = function() m
+  setinv = function(mi) inv <<- mi
+  getinv = function() inv
+  
+  res = list(set = set, get = get, setinv = setinv, getinv = getinv)
+  res$set(x)
+  res
 }
 
 
-## Write a short comment describing this function
+## Computes the inverse: gest from cache if it is computed or computes it, if it is not
+## Returns the inverse
 
 cacheSolve <- function(x, ...) {
         ## Return a matrix that is the inverse of 'x'
+  
+  inv = x$getinv()
+  if (!is.null(inv))
+  {
+    message ("getting cached data")
+    return(inv)
+  }
+  mat = x$get()
+  inv = solve(mat)
+  x$setinv(inv)
+  inv
 }

From 100fda0f7e1aeebfb16758ba2c93c55521d5cefc Mon Sep 17 00:00:00 2001
From: Miguel Rocha <mrocha@di.uminho.pt>
Date: Mon, 21 Apr 2014 18:33:13 +0100
Subject: [PATCH 2/2] solved the assignment

---
 cachematrix.R | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/cachematrix.R b/cachematrix.R
index 810872a0c73..78d7c10ede5 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -7,17 +7,24 @@
 
 makeCacheMatrix <- function(x = matrix()) {
   inv = NULL
+  ## set function
   set = function(mat)
   {
     m <<- mat
     inv <<- NULL
   }
+  # get function
   get = function() m
+  # setinv function
   setinv = function(mi) inv <<- mi
+  # getinv function
   getinv = function() inv
   
+  # builds the list
   res = list(set = set, get = get, setinv = setinv, getinv = getinv)
+  # needed to store the matrix when creating cache
   res$set(x)
+  # returns the list
   res
 }
 
@@ -29,13 +36,22 @@ cacheSolve <- function(x, ...) {
         ## Return a matrix that is the inverse of 'x'
   
   inv = x$getinv()
+  ## if inverse is calculated return cached inverse
   if (!is.null(inv))
   {
     message ("getting cached data")
     return(inv)
   }
+  ## else compute it and return it
   mat = x$get()
   inv = solve(mat)
   x$setinv(inv)
   inv
 }
+
+## example code to run
+## m1 = matrix(rnorm(16), 4, 4)
+## cm1 = makeCacheMatrix(m1)
+## cacheSolve(cm1)
+## cacheSolve(cm1)
+## second run gets the result from cache