colorbar not working?

clc;
close all;
clear;

x = -1:2/511:1;

[X,Y] = meshgrid(x);

R = sqrt(X.^2 + Y.^2);
Phi = atan2(X,Y);
Z = zeros(512,512);

index1 = find(Phi<pi/20 & Phi>-pi/20);
Z(index1)=6;

index2 = find(R<0.0142);
Z(index2)=50;

index3 = find(R>0.425);
Z(index3)=0;

surf(X,Y,Z)
colorbar 

%view(2)

Any idea why the plot comes up all black?

Thanks

S

[Dyuman Joshi]

"Any idea why the plot comes up all black?"

Because your mesh is extremely dense. I have increased the mesh density by 5 times, so to can see the corresponding result.

However, if you want a refined surface/mesh, you can hide the grid lines, as @Voss has shown.

Also, note that you should not hard code values, as that is likely to cause issues - In this case while defining Z. And you can use logical indexing instead of find(), as it is more efficient.

x = -1:2*5/511:1;

[X,Y] = meshgrid(x);

R = sqrt(X.^2 + Y.^2);
Phi = atan2(X,Y);

%Define Z according to the size of R, instead of hard-coding
Z = zeros(size(R));

%logical indexing

index1 = (Phi<pi/20 & Phi>-pi/20);
Z(index1)=6;

index2 = (R<0.0142);
Z(index2)=50;

index3 = (R>0.425);
Z(index3)=0;

surf(X,Y,Z)
colorbar 

%view(2)

[sxh]

Mesh density is not the problem here..

Thanks for the answer tho :)

Answer 1

[Voss]

The black you see is grid lines of the surface. You can turn them off by setting the surface EdgeColor property to 'none'.

clc;
close all;
clear;

x = -1:2/511:1;

[X,Y] = meshgrid(x);

R = sqrt(X.^2 + Y.^2);
Phi = atan2(X,Y);
Z = zeros(512,512);

index1 = find(Phi<pi/20 & Phi>-pi/20);
Z(index1)=6;

index2 = find(R<0.0142);
Z(index2)=50;

index3 = find(R>0.425);
Z(index3)=0;

surf(X,Y,Z,'EdgeColor','none')
colorbar 

% view(2)