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Author: jamesmcm

cachematrix.R

@@ -1,15 +1,52 @@
-## Put comments here that give an overall description of what your
-## functions do
+## These functions allow one to calculate and cache a matrix inverse,
+## avoiding the need to recalculate the inverse if it is needed multiple times.
 
-## Write a short comment describing this function
+### Example:
+### > source("./cachematrix.R")
+### > mymat <- makeCacheMatrix(matrix(c(1,2,3,3,2,1,4,5,2),ncol=3,nrow=3))
+### > cacheSolve(mymat)
+###        [,1]   [,2]    [,3]
+### [1,] -0.0625 -0.125  0.4375
+### [2,]  0.6875 -0.625  0.1875
+### [3,] -0.2500  0.500 -0.2500
+###
+### > cacheSolve(mymat)
+### getting cached data
+###        [,1]   [,2]    [,3]
+### [1,] -0.0625 -0.125  0.4375
+### [2,]  0.6875 -0.625  0.1875
+### [3,] -0.2500  0.500 -0.2500
 
+
+## This creates the matrix object that will store the cached inverse, and a method to calculate the inverse
 makeCacheMatrix <- function(x = matrix()) {
+  i <- NULL
+  set <- function(y) {
+    x <<- y
+    i <<- NULL
+  }
+  get <- function() x
+  setinv <- function(inv) i <<- inv
+  getinv <- function() i
 
+  return( list(set = set, get = get,
+               setinv = setinv,
+               getinv = getinv)  )
 }
 
 
-## Write a short comment describing this function
-
+## This function will return the inverse of a matrix, via the cached value if possible
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  ## Return a matrix that is the inverse of 'x'
+
+  i <- x$getinv()
+  if(!is.null(i)) {
+    message("getting cached data")
+    return(i) #if we already cached inverse then return and stop here
+  }
+  #otherwise calculate and cache inverse
+  data <- x$get()
+  i <- solve(data, ...) #solve for inverse - R function
+  x$setinv(i) #cache inverse
+  return(i)
 }