How to plot a 3D surface out of points, and set explicit colors for specific value ranges

I have matrices x, y, z, and s, which have dimensions 2500x1. I'm trying to make a surface plot out of x, y, z. I tried this:https://www.mathworks.com/matlabcentral/answers/384291-3d-surface-plot-out-of-points#answer_306637. But is it possible to set plot colors for specific value ranges of s (given in the table below)? Like by applying a colormap or something?

I have defined the colormap as follows:

map = [0  1  0;
       0  1  1;
       0  0  1;
       0 0.5 1;
       1  1  1;
       1  1 0.5;
       1  1  0;
       1 0.5 0;
       1  0  0];
    
colormap(map);
caxis([-1 1]);

As an example, I need the plot to look similar to this:

[darova]

Your code looks correct. What is the problem?

[Batyrkhan Tokmyrza]

I can't get the colors right. I was thinking that maybe someone could give a hint on how to correctly pass the colormap into the trisurf() function, or suggest a different method of plotting. This is my code:

dt = delaunayTriangulation(x,y);
tri = dt.ConnectivityList;
xi = dt.Points(:,1);
yi = dt.Points(:,2);
F = scatteredInterpolant(x,y,z);
zi = F(xi,yi);

map = [0  1  0;
       0  1  1;
       0  0  1;
       0 0.5 1;
       1  1  1;
       1  1 0.5;
       1  1  0;
       1 0.5 0;
       1  0  0];

figure
surface = trisurf(tri,xi,yi,zi);
shading interp
colormap(map);
caxis([-1 1]);
grid on
colorbar
hold on

This is what I'm getting, which is not correct:

Answer 1

[Ameer Hamza]

It is obvious from your image that you are not setting the limits of caxis properly. Your code

caxis([-1 1]);

but your image show that value vary in range [-4000, 4000]

Try

caxis([-4000 4000]);

[Batyrkhan Tokmyrza]

But s is supposed to be between [-1 1], not [-4000 4000]. The color needs to be tied to the values of s, not z.

[Ameer Hamza]

Can you show your code? How is variable s being used?

[Batyrkhan Tokmyrza]

Well, s isn't being used at the moment. That's what I can't figure out how to use with a 3D surface. I have a text file with the surface data, where each row has 4 values separated by commas (x, y, z, and s respectively). My code:

clear all;

path_to_txt = 'Surface_Data.txt';
surface_data = readtable(path_to_txt);

x = table2array(surface_data(:,1));
y = table2array(surface_data(:,2));
z = table2array(surface_data(:,3));
s = table2array(surface_data(:,4));

dt = delaunayTriangulation(x,y);
tri = dt.ConnectivityList;
xi = dt.Points(:,1);
yi = dt.Points(:,2);
F = scatteredInterpolant(x,y,z);
zi = F(xi,yi);

map    = [ 0  1  0 ;
           0  1  1 ;
           0  0  1 ;
           0 0.5 1 ;
           1  1  1 ;
           1  1 0.5;
           1  1  0 ;
           1 0.5 0 ;
           1  0  0 ];  

figure
surface = trisurf(tri,xi,yi,zi);
shading interp
colormap(map);
caxis([-1 1]);
grid on
colorbar
hold on

[Ameer Hamza]

The color is taken from the colormap according to whatever variable is on the z-axis and the value of CLim for the color axis. If you want the colormap to be linked to s, then you need to use s in place of z in your code.

What do the four columns of your dataset represent? Maybe that can help in determining how the s value can be used.

Answer 2

[Walter Roberson]

Your map is wrong. You did not take into account that the first and last slots are half the size of the other slots.

map    = [ 0  1  0 ;   %-1 to -7/8    %green
    
           0  1  1 ;   %-7/8 to -6/8  %cyan
           0  1  1 ;   %-6/8 to -5/8
           
           0  0  1 ;   %-5/8 to -4/8  %blue
           0  0  1 ;   %-4/8 to -3/8
           
           0 0.5 1 ;   %-3/8 to -2/8  %pale blue
           0 0.5 1 ;   %-2/8 to -1/8
           
           1  1  1 ;   %-1/8 to 0     %white
           1  1  1 ;   %0 to +1/8
           
           1  1 0.5;   %+1/8 to +2/8  %pale yellow
           1  1 0.5;   %+2/8 to +3/8
           
           1  1  0 ;   %+3/8 to +4/8  %yellow
           1  1  0 ;   %+4/8 to +5/8
           
           1 0.5 0 ;   %+5/8 to +6/8  %orange
           1 0.5 0 ;   %+6/8 to +7/8
           
           1  0  0 ];  %+7/8 to +1   %red

[Batyrkhan Tokmyrza]

And do you have any ideas as to how to do I tie this to the values of s?

[Ameer Hamza]

I provided the same solution to OP's other question here: https://www.mathworks.com/matlabcentral/answers/510757-how-to-set-explicit-contour-plot-colors-for-specific-value-ranges?s_tid=prof_contriblnk but here the issue seems to be about the limits of color axis.