Unable to plot inequality region

This is the solution I am trying to mimic, but for my case it does not seem to work:

syms ki kd
cond = [ -9*ki, 10*ki - 10*kd + 10, 360*kd - 24*ki + 1320]; % My 3 inequality conditions

Unrecognized function or variable 'ki'.

r = -5:0.01:5;
[ki, kd] = meshgrid(r);

condition1 = cond(1) > 0;
condition2 = cond(2) > 0;
condition3 = cond(3) > 0;

output = ones(length(r));
output(~(condition1 & condition2 & condition3)) = 0; % this fails

imshow(output, 'xdata', r, 'ydata', r);

axis on;

the line that fails gives me this error:

Error using symengine

Unable to prove '~0 < -9*ki | ~0 < 10*ki - 10*kd + 10 |

~0 < 360*kd - 24*ki + 1320' literally. Use 'isAlways' to

test the statement mathematically.

Error in sym/subsindex (line 841)

X =

find(mupadmex('symobj::logical',A.s,9)) -

1;

How can I solve this? It seems like it should be such a simple thing to do, but I can't make it work.

Answer 1

[KSSV]

r = -5:0.01:5;
[ki, kd] = meshgrid(r);
cond =  -9*ki>0 & 10*ki - 10*kd + 10>0 & 360*kd - 24*ki + 1320>0; % My 3 inequality conditions

% output = ones(length(r));
% output(~(condition1 & condition2 & condition3)) = 0; % this fails

imshow(cond, 'xdata', r, 'ydata', r);

axis on;

[YLieven]

What if I wanted a surf plot instead of imshow?

I want it to become something like this:

with the "Z" coordinate fixed in a specific value (like -1 in the image above).

[KSSV]

Replace zeros with Nan and use surf.

[YLieven]

It works! Thank you.