Function bodies

Author: Bruno Marques

cachematrix.R

@@ -1,15 +1,33 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Functions for creating an object that stores a matrix and its inverse, when calculated.
+## When the matrix is changed, the inverse cache is nullified.
 
-## Write a short comment describing this function
+## Creates a wrapping object around a matrix that can store a cache of its inverse
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  inv <- NULL # contains the cached inverse
+  set <- function(y) { # sets a new value and nullifies the inverse cache
+    x <<- y
+    inv <<- NULL
+  }
+  get <- function() x # retrieves the matrix
+  setinverse <- function(inverse) inv <<- inverse # sets the inverse cache
+  getinverse <- function() inv # retrieves the cached inverse
+  list(set=set, get=get, setinverse=setinverse, getinverse=getinverse)
 }
 
 
-## Write a short comment describing this function
+## Tries to retrieve the inverse matrix of an object created by makeCacheMatrix,
+## and calculates it if necessary
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  inv <- x$getinverse()
+  if(!is.null(inv)) {
+    # the inverse is already known; no need to recalculate
+    message("getting cached data")
+    return(inv)
+  }
+  data <- x$get()
+  inv <- solve(data, ...) # calculates the inverse matrix
+  x$setinverse(inv) # caches the inverse matrix for future use
+  inv
 }