Troubleshooting - A Guide to MATLAB for Beginners and Experienced Users - page 279

the idea is to fill the largest circle in black, then fill the next largest circle in
white leaving only a ring of black, then fill the next largest circle in black
leaving a ring of white, etc. The if statement tests true when r is odd and
false when it is even. We stop the alternation of black and white at a radius
of 2 to make the last circle red instead of black; then we adjust the axes to
make the circles appear round.

t = linspace(0, 2*pi, 100);
cla reset; hold on
for r = 21:-1:2
if mod(r, 2)
fill(r*cos(t), r*sin(t), 'k')
else
fill(r*cos(t), r*sin(t), 'w')
end
end
fill(cos(t), sin(t), 'r')
axis equal; hold off

20

15

10

5

0

− 5

− 10

− 15

− 20

− 25 − 20 − 15 − 10 − 5 0 5 10 15 20 25

Problem 6
Here are the contents of our solution M-file:

function m = mylcm(varargin)
nums = [varargin { : } ];
if ~ isnumeric(nums) any(nums ~ = round(real(nums))) ...
any(nums <= 0)