# surface plot

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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.

##### 0 Comments

### Answers (3)

Grzegorz Knor
on 29 Nov 2011

[a b] = meshgrid(0:.1:1,0:.01:.1);

c = a + b;

surfl(a,b,c)

##### 1 Comment

Walter Roberson
on 29 Nov 2011

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.

##### 0 Comments

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:

[num, txt]= xlsread('rank.xlsx', 'A2:C72');

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.

##### 11 Comments

Walter Roberson
on 6 Apr 2019

Perhaps you would prefer a different approach:

num = xlsread('rank.xlsx', 'A2:C10745');

x = num(:,1);

y = num(:,2);

z = num(:,3);

K = boundary(x, y, z, 1);

trisurf(K, x, y, z);

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