Redid the assignment as a refresher

cachematrix.R

@@ -1,15 +1,61 @@
-## Put comments here that give an overall description of what your
-## functions do
+# Written by Larry Mannings, 25 November 2025
 
-## Write a short comment describing this function
-
-makeCacheMatrix <- function(x = matrix()) {
+# makeCacheMatrix() function leverages the makeVector example from R Programming
+# Ass. 2, modified to create a list consisting of cached matrix and 
+# corresponding inverse.
 
+makeCacheMatrix <- function(x = numeric()) {
+
+    # x is numeric matrix object representing an invertible matrix
+    # i is matrix object representing inverse of matrix object (x)
+
+    # Initialize the inverse matrix to NULL
+    i <- NULL
+
+    # Set the value of the matrix
+    set <- function(y) {
+        x <<- y
+        i <<- NULL
+    }
+    # Get the value of the matrix
+    get <- function() x
+
+    # Set the value of the inverse matrix
+    setinv <- function(inv) i <<- inv
+
+    # Get the value of the inverse matrix
+    getinv <- function() i
+
+    # Store objects in a list and return
+    list(set = set, get = get,
+         setinv = setinv,
+         getinv = getinv)
 }
 
 
-## Write a short comment describing this function
+#---------------------------------------------------------------------------
+
+# cacheSolve() function leverages the cachemean() example from R Programming
+# Ass. 2, modified to compute the inverse of the returned by 
+# makeCacheMatrix() function.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
-}
+
+    # x is list object representing constructed from the makeCacheMatrix 
+    # function
+    # i is matrix object representing inverse of matrix object (x)
+
+    # Call the getinv(function) as a list object to get matrix inverse 
+    i <- x$getinv()
+    # If the inverse has already been calculated retrieve from the cache
+    if(!is.null(i)) {
+        message("getting cached data")
+        return(i)
+    }
+    # Else, retrieve the cached matrix and solve for the inverse matrix
+    data <- x$get()
+    i <- solve(data, ...)
+    # Cache the inverse matrix and return value
+    x$setinv(i)
+    i
+}