first version of cachematrix.R

Author: mantour

cachematrix.R

@@ -1,15 +1,90 @@
 ## Put comments here that give an overall description of what your
 ## functions do
+#
+# makeCacheMatrix creates a special "matrix", which is really a list 
+# containing  functions to
+#
+# 1 set the value of the matrix
+# 2 get the value of the matrix
+# 3 set the value of the inverse
+# 4 get the value of the inverse
+#
+# cacheSolve solve the inverse of the input "matrix", in the manner that 
+#
+# 1. return the cached inverse if the cache is not NULL
+# 2. calculate the inverse with solve if the cache is NULL, set it to the cache, 
+#    and then return it
+#
+# Example:
+# > A<-matrix(c(1,2,3,4),c(2,2))
+# > B<-makeCacheMatrix(A)
+# > B$get()
+#       [,1] [,2]
+# [1,]    1    3
+# [2,]    2    4
+# > cacheSolve(B)
+#       [,1] [,2]
+# [1,]   -2  1.5
+# [2,]    1 -0.5
+# > cacheSolve(B)
+# getting cached data
+#       [,1] [,2]
+# [1,]   -2  1.5
+# [2,]    1 -0.5
+#
+
+
 
 ## Write a short comment describing this function
+#
+# creates a special "matrix", which is really a list 
+# of the following functions  
+#
+# set(y) set y as the data of the matrix
+# get() : get the data of the matrix
+# setinverse(): set the value of the inverse
+# getinverse(): get the value of the inverse
+#
+# arguments:
+# x is a matrix to be set as the "data" of the special matrix
 
 makeCacheMatrix <- function(x = matrix()) {
+    inv <- NULL
+    set <- function(y){
+        x <<- y
+    }
+    get <- function() x
 
+    setinverse <- function(inverse){
+        inv <<-inverse
+    }
+    getinverse <- function() inv
+    
+    list(set = set, get=get, setinverse = setinverse, getinverse=getinverse)
+    
 }
 
 
 ## Write a short comment describing this function
+#
+#  return the cached inverse and print a message, 
+#  calculate the inverse with solve and set it to the cache otherwise
+#
+#  arguments:
+#  x is a special matrix created by makeCacheMatrix
+#  ... is the other options that will be passed to "solve"
+#
 
 cacheSolve <- function(x, ...) {
         ## Return a matrix that is the inverse of 'x'
+    inv <- x$getinverse()
+    if(!is.null(inv)){
+        message("getting cached data")
+    }
+    else{
+        data <- x$get()
+        inv <- solve(data,...)
+        x$setinverse(inv)
+    }
+    inv
 }