Surf function with interp: symmetric surface shown assymmetrically

Question

kandaz 2018-11-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/430416-surf-function-with-interp-symmetric-surface-shown-assymmetrically

评论： kandaz 2018-11-18

Hello All,

I have a surface Z formed by the following commands (very simplified version) and it is symmetric in XY plane (looking from the top or bottom). However when I use the "surf" command with 'interp', I get a slightly assymetric surface.

clc
clear all
Z=[0 0.1 0.3 0.1 0;
   0 0.2198 0.4432532 0.2198 0;
   0 0.4242 0.7898989 0.4242 0;
   0 0.2198 0.4432532 0.2198 0;
   0 0.1 0.3 0.1 0];
[X,Y] = meshgrid(0:1.5:6,0:1.5:6);
surf(X, Y, Z, 'LineStyle', '-', 'FaceColor', 'interp')
daspect([1,1,0.2])
colormap(jet)
colorbar

When I use decimal numbers instead of the Z values above though, I do not get such a problem.

Any ideas how to obtain the symmetric surface at XY plane?

Cheers.

2 个评论
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Stephen23 2018-11-17

Ugh, jet colormap:

https://blogs.mathworks.com/headlines/2018/10/10/a-dangerous-rainbow-why-colormaps-matter/

https://blogs.mathworks.com/steve/2014/10/13/a-new-colormap-for-matlab-part-1-introduction

https://blogs.mathworks.com/steve/2014/10/20/a-new-colormap-for-matlab-part-2-troubles-with-rainbows/

Bruno Luong 2018-11-17

IMO Parula does not releal defect as clear as JET (which I still prefer in general)

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Answer 1

Bruno Luong 2018-11-17

3
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/430416-surf-function-with-interp-symmetric-surface-shown-assymmetrically#answer_347490

编辑：Bruno Luong 2018-11-17

在 MATLAB Online 中打开

The color interpolation carried out by MATLAB is not symetric by values but also by order. This induces the defect.

To trick MATLAB you have te reorganize the data

Z=[0 0.1 0.3 0.1 0;
   0 0.2198 0.4432532 0.2198 0;
   0 0.4242 0.7898989 0.4242 0;
   0 0.2198 0.4432532 0.2198 0;
   0 0.1 0.3 0.1 0];
[X,Y] = meshgrid(0:1.5:6,0:1.5:6);
x = linspace(-1,1,size(Z,2));
y = linspace(-1,1,size(Z,1));
close all
hold on
for k=1:4
    if k<=2
        ix = find(x>=0);
    else
        ix = flip(find(x<=0));
    end
    if mod(k,2)==0
        iy = find(y>=0);
    else
        iy = flip(find(y<=0));
    end   
    surf(X(iy,ix), Y(iy,ix), Z(iy,ix), 'LineStyle', '-', 'FaceColor', 'interp')
end
daspect([1,1,0.2])
colormap(jet)
colorbar