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Author: btedev

cachematrix.R

@@ -1,15 +1,50 @@
-## Put comments here that give an overall description of what your
-## functions do
+## To speed performing repeated inversions of matrices, the functions
+## below will cache the first inversion and return the contents
+## of the cache for repeated calls.
 
-## Write a short comment describing this function
+## Creates a list that has functions to set a matrix, get the matrix,
+## set the inverse of the matrix, and get the inverse of the matrix.
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  inverse <- NULL
+  set <- function(y) {
+    x <<- y
+    inverse <<- NULL
+  }
+  get <- function() x
+  setinverse <- function(i) inverse <<- i
+  getinverse <- function() inverse
+  list(set=set, get=get, setinverse=setinverse, getinverse=getinverse)
 }
 
 
-## Write a short comment describing this function
+## Computes the inverse of a "matrix" object created by makeCacheMatrix.
+## If the inverse has already been calculated, it will be returned
+## from the cache.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  inverse <- x$getinverse()
+  if(!is.null(inverse)) {
+    message("getting cached data")
+    return(inverse)
+  }
+  data <- x$get()
+  inverse <- solve(data, ...)
+  x$setinverse(inverse)
+  inverse
 }
+
+## My test of the functions:
+#
+# > source("cachematrix.R")
+# > mcm <- makeCacheMatrix(x=matrix(c(4,7,2,6), nrow=2, ncol=2, byrow=T))
+# > cacheSolve(mcm)
+      #[,1] [,2]
+# [1,]  0.6 -0.7
+# [2,] -0.2  0.4
+# > cacheSolve(mcm)
+# getting cached data
+      #[,1] [,2]
+# [1,]  0.6 -0.7
+# [2,] -0.2  0.4
+