Cleve Moler's mandelbrot.m gives errors in Matlab R2019b

In the book "Experiments with Matlab" of Cleve Moler (free ebook)

Cleve Moler : Experiments with matlab

with source code

Experiments with matlab - source code

is an experiment mandelbrot.m.

When you run it, you should get a graphical menu.

It worked fine in R2017a, but now in R2019b there seem to be checks that are more strict:

>> mandelbrot
Error:File: mandelbrot.m Line: 54 Column: 14
Identifier 'depth' is not a function or a shared variable. To share 'depth' with nested function, 
initialize it in the current scope. For more information, see Sharing Variables Between Parent and Nested Functions.

I have no clue where and what to change.

Do you know / have experience in what changed recently in matlab R2019b?

[Bert RAM Aerts]

Well in fact I was investigating how to use my nVIDIA GPU for Mandelbrot fractals. And I just found:

Illustrating Three Approaches to GPU Computing: The Mandelbrot Set

Very nice improvement factors.

Answer 1

[Bert RAM Aerts]

Solution is very simple, just add following global variables to mandelbrot.m:

% to make R2019b happy (global variables)
depth = 0;
width = 0;
z = 0;
kz = 0;
center = 0;
cmapidx = 0;

% Switchyard.
...