Committing the assignment code

Author: drdrsh

cachematrix.R

@@ -1,15 +1,107 @@
-## Put comments here that give an overall description of what your
-## functions do
+# Author:
+#   Mostafa Abdelraouf <[email protected]>
+# Description:
+#   Peer assessment assignment (Programming Assignment 2) submission
+#   for JHU R programming course
+#   https://class.coursera.org/rprog-016/human_grading/view/courses/973757/assessments/3/submissions
+#  
+# Notes:
+#   1) I have strayed a bit from the requirements of the assignment for sake
+#   of encapsulation and to not clutter the global namespace.
+#   I have encapsulated the function that caches the inverse matrix inside the 
+#   returned object. The user of this object will not be required to explicitly call "cacheSolve".
+#   Instead, if the user needs to get the inverse matrix he will just have to call
+#   GetInverse(), it will calculate and cache the result and any further calls will be
+#   served the cached inverse directly.
+#  2) This file uses, to the best of my ability, Google's R Style guide
+#   http://google-styleguide.googlecode.com/svn/trunk/Rguide.xml 
 
-## Write a short comment describing this function
+MakeCacheMatrix <- function(x=matrix()) {
+  # Creates a matrix object that supports inverse matrix calculation and caching 
+  #
+  # Args:
+  #	x: A matrix to build the object around,note that the matrix is assumed
+  #		to be invertable.
+  #
+  # Returns:
+  #	A list of functions (Or rather, an object) that can be used to modify
+  #	the matrix
 
-makeCacheMatrix <- function(x = matrix()) {
+ 
+  # Check if the x parameter is a matrix, if not, prints an error 
+  # message and exits
+  if (!is.matrix(x)){
+    message("Parameter supplied to makeMatrix() MUST be a matrix")
+    return (NULL)
+  }
 
-}
+  original.matrix <- x
+  inverse.matrix <- NULL	# This will hold our inverse matrix
+ 
+  Set <- function(x) {
+    # Sets the value of the internal matrix and invalidates the cache.
+    #
+    # Args:
+    #	x: A matrix to build the object around,note that the matrix is assumed
+    #		to be invertable.
+    #
+    # Returns:
+    #	True on success, false of failure
 
+    # if y is not a matrix, we output an error message and make no changes to
+    # the internal matrix
+    if (!is.matrix(x)){
+      message("Parameter supplied to Set() MUST be a matrix")
+      return (FALSE)
+    }
+  
+    original.matrix <<- x # change the value of the internal matrix to "y"
+    
+    # Notice that when resetting the internal matrix we invalidated any previously 
+    # stored "inverse" by setting it to null
+    inverse.matrix <<- NULL
+    
+    message("Resetting internal matrix, cache is now invalid")
+    
+    TRUE
+  }
 
-## Write a short comment describing this function
+  Get <- function(){
+    # Gets the internal matrix
+    #
+    # Returns:
+    #	a copy of the internal matrix
+    original.matrix
+  }
 
-cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
-}
+  GetInverse <- function(){
+    #	Calculates, caches and returns the inverse matrix of the internal matrix using (solve() function)
+    #
+    # Returns:
+    #	the inverse matrix of the internal matrix using (solve() function) 
+    
+    # Check to see if we have a valid "inverse matrix" cache for our matrix
+    # if so, return it immediately 
+    if (!is.null(inverse.matrix)){
+      message("Returning cache")
+      return(inverse.matrix)
+    }
+    
+    # Otherwise, generate the inverse cache and store it internally in the "inverse.matrix" variable
+    message("No cache found, generating cache")
+    inverse.matrix <<- solve(original.matrix)
+    
+    #return the inverse
+    inverse.matrix
+    
+  }
+
+  # This will return a list containing 3 functions that can be used to manipulate this particular
+  # instance of the matrix
+  list(
+    Set = Set, 
+    Get = Get,
+    GetInverse = GetInverse
+  )
+  
+}

cachematrix_output.R

@@ -0,0 +1,45 @@
+# Author:
+#   Mostafa Abdelraouf <[email protected]>
+# Description:
+#   Output of the Peer assessment assignment (Programming Assignment 2) submission
+#   for JHU R programming course
+#   https://class.coursera.org/rprog-016/human_grading/view/courses/973757/assessments/3/submissions
+#
+
+source('cachematrix.R');
+
+a <- c(100,50,90)
+b <- c(200,42,99)
+c <- c(77,56,34)
+
+d <- c(105,33,80)
+e <- c(240,22,59)
+f <- c(78,33,39)
+
+# Create our matrix
+m1 <- MakeCacheMatrix(rbind(a,b,c))
+message("Original Matrix")
+print(m1$Get())
+
+# This call will not find a cached matrix and thus will generate it
+message("Inverted Matrix")
+print(m1$GetInverse())
+
+# All subsequent calls to "getInverse" will use the cached inverse matrix
+print(m1$GetInverse())
+print(m1$GetInverse())
+print(m1$GetInverse())
+
+# The following call will change the matrix and invalidate the cache
+m1$Set(rbind(d,e,f))
+message("Original Matrix")
+print(m1$Get())
+
+# This call will not find a cached matrix and thus will generate it
+message("Inverted Matrix")
+print(m1$GetInverse())
+
+# All subsequent calls to "getInverse" will use the cached matrix
+print(m1$GetInverse())
+print(m1$GetInverse())
+print(m1$GetInverse())