# surface plot

21 views (last 30 days)
Bahareh on 29 Nov 2011
Commented: Albert J. G. on 6 Apr 2019
Hello all,
I have the following code:
a = 0:.1:1;
b = 0:.01:.1;
for k = 1:length(a)
c = a(k) + b(k);
end
I would like to plot 'c' versus 'a' and 'b' using 'surfl'; Is there a way to do it? thanks.

Grzegorz Knor on 29 Nov 2011
[a b] = meshgrid(0:.1:1,0:.01:.1);
c = a + b;
surfl(a,b,c)
Walter Roberson on 29 Nov 2011
Bahareh's previous question was specifically asking about combining a(K) and b(K) instead of producing a grid, so it seems your code (fine in most circumstances) is not what is desired _here_

Walter Roberson on 29 Nov 2011
a = 0:.1:1;
b = 0:.01:.1;
c = a + b;
t = nan(length(a),length(a));
z = diag(c) + tril(t,-1) + triu(t,1); %defined on diag, else nan
surfl(a,b,z);
I would not expect the plot to have any useful content, though. surface plots do interpolation from vertices to determine what to draw, but you are only defining the result along a line.
I will not suggest that you want the entire grid of a(J) + b(K) values as that would not be in accordance with your previous question.

Albert J. G. on 17 Mar 2019
This question is about how to plot a surface diagram.
The data are in an excel file, as you can find.
My question is how to plot a surface diagram using data from A2 to C72? (if you think data is no enough, you can use C491)
Maybe x=kp; y = ki; z = delay. What I need is like surf(x,y,z), and it will give a surface plot with NO ERROR (this is the most important, I think).
This is the question borthering me for a long time.
BTW, it not hard to plot a 3D scattor diagram, using:
x = num(:,1);
y = num(:,2);
z = num(:,3);
% the point on 3d diagram:
plot3(x,y,z,'.','color','black','markersize',12)
xlabel('kp')
ylabel('ki')
zlabel('delay')
grid on
But I really donnot how to plot a surface since Z do not have a obvious relation with X and Y.
Walter Roberson on 6 Apr 2019
Perhaps you would prefer a different approach:
x = num(:,1);
y = num(:,2);
z = num(:,3);
K = boundary(x, y, z, 1);
trisurf(K, x, y, z);
Albert J. G. on 6 Apr 2019
Wow! That works!! Thx!!!

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