MATLAB doesn't give an answer for this Waterfall graph and runs this continuously, what's wrong with this?

a = linspace(0.01, 10, 4001);
r = linspace(0.1, 10, 4001);

for i = 1:numel(a)
    for j = 1:numel(r)
        X(i, j)=(a(i)*r(j)^2)/((r(j)^3)-(a(i))*r(j)+a(i));
    end
end

figure;
waterfall(r, a, X');
xlabel('r');
ylabel('a');
zlabel('X');
title('3D Waterfall Plot for X=(a*r^2)/((r^3)-(a)*r+a)');

Answer 1

[Walter Roberson]

You need to vectorize

Reduced size here to fit within the time limits.

a = linspace(0.01, 10, 401);
r = linspace(0.1, 10, 401);

X = (a(:).*r.^2) ./ ((r.^3) - (a(:)) .* r + a(:));

figure;
waterfall(r, a, X');
xlabel('r');
ylabel('a');
zlabel('X');
title('3D Waterfall Plot for X=(a*r^2)/((r^3)-(a)*r+a)');

[Yuvraaj Pasumarthy]

thanks for the prompt reply!

Just had another question, If I want to apply the log function to X, how do I do it? I tried to but yet again the graph is not loading...

[Walter Roberson]

X has negative values. Log of negative values is complex, and waterfall cannot construct plots with complex coordinates.

In the below, I set those coordinates to NaN.

a = linspace(0.01, 10, 401);
r = linspace(0.1, 10, 401);

X = (a(:).*r.^2) ./ ((r.^3) - (a(:)) .* r + a(:));

figure;
Lx =  log(X);
Lx(imag(Lx)~=0) = nan;
waterfall(r, a, Lx');
xlabel('r');
ylabel('a');
zlabel('X');
title('3D Waterfall Plot for X=(a*r^2)/((r^3)-(a)*r+a)');

[Yuvraaj Pasumarthy]

thank you so much for your help sir!