Working code tested on invertable matrices

gregoryg · gregoryg · commit bc359ce72a77 · 2014-11-21T23:37:41.000-07:00
diff --git a/cachematrix.R b/cachematrix.R
@@ -1,15 +1,34 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
-
+## Create a matrix and lexically scoped function 
+## Follow the code in the example for this assignment
+## ???
+## Profit!
+## Pass in matrix, return list with setters and getters
+## test on example from forum: matrix(c(1,1,1,3,4,3,3,3,4),3,3)  
+## more tests at https://class.coursera.org/rprog-009/forum/thread?thread_id=164
 makeCacheMatrix <- function(x = matrix()) {
-
+    invertedMatrix <- NULL
+    set <- function(y) {
+        x <<- y
+        invertedMatrix <<- NULL
+    }
+    get <- function() x
+    setinverse <- function(inverse) invertedMatrix <<- inverse
+    getinverse <- function() invertedMatrix
+    list(set = set, get = get, setinverse = setinverse, getinverse = getinverse) ## list with function closures!
 }
 
-
-## Write a short comment describing this function
-
+## Use the R solve() function to invert a matrix - return prior results if cached
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    ## Return a matrix that is the inverse of 'x'
+    ## NO CHECKING for invertable matrix
+    invertedMatrix <- x$getinverse()
+    if (!is.null(invertedMatrix)) {  ## if not null, we found a cache hit
+        message("getting cached matrix")
+        return(invertedMatrix)
+    } else {  ## cache miss; else clause clearer IMO
+        invertedMatrix <- solve(x$get()) ## execute the function, don't return it
+        x$setinverse(invertedMatrix) ## now set the cache so we don't recalculate on another invocation
+        return(invertedMatrix)
+    }
 }
+
