Change size 3D matrix

Hi, I have a 3D matrix defined as: EP(N,k,r) and I want to plot its values as different surfaces at constant N. So I tried to plot this matrix in this way:

col=hsv(N);
figure
hold on
for f=1:N
    surf(vector_1,vector_2,EP(f,:,:),'Color',col(f,:,:));
    legendInfo{f} = [num2str(Temp(f)-273.15) ' °C'];
end
legend(legendInfo)

but it doesn't work. It seems I can only plot surfaces at constant r! So now I want to try to plot a new matrix in the form (k,r,N).

How can I change the dimension of matrix EP(N,k,r) (and so its values inside) in this form: EP_1(k,r,N)?

[darova]

You want to plot slices of a volume?

[Francesco Guaresi]

I want to plot surfaces. Different surfaces at different value of "N". So in the x-axis I have a vector of size k, in y axis a vector of size r, and in the third axis the values of matrix EP (at constant "N").

[darova]

What about slice or volumeslice?

[Francesco Guaresi]

I think I need “slices”. Actually, I want something like in this picture: different surfaces in a 3D plot

[the cyclist]

When you say, "it doesn't work", what do you mean, specifically? Do you mean that the code runs, but gives an unexpected result, or that the code does not run, and gives an error? If that latter, please post the complete error message.

[Francesco Guaresi]

The entire code works, except this plot. The error message is:

Error using surf (line 71)

Z must be a matrix, not a scalar or vector.

Error in Isothermal_PFR_EP3_tensor_plot_3D (line 437)

surf(vector_1,vector_2,EP(f,:,:),'Color',col(f,:,:));

Answer 1

[the cyclist]

I think what you want is to use

permute(EP(f,:,:),[2 3 1])

as the input, instead of just EP(f,:,:), so that you have a 2-d matrix, rather than a 3-d (in which the first dimension has length 1).

[Francesco Guaresi]

I've obtained this graph, but I need a 3D graph:

[the cyclist]

Can you upload the variables that you are using to make the plot, in a *.mat file?

[Francesco Guaresi]

Yes! I've written this matlab file (the original one is more long):

clc
clear all
close all

Temp = [600 650 700 750] + 273.15;
xV_vector = [.2 .3 .4 .5 .6];
H_D_ratio = [6 7 8 9 10];

N = max(size(Temp));
k = max(size(xV_vector));
r = max(size(H_D_ratio));

col=hsv(N);

% EP3 matrix is generated by other computations in my original matlab file,
% here below the values obtained:

EP3(:,:,1) = 1.0e+06 * [2.4819    2.7183    2.2334    1.1416   -0.8249;
                        3.7156    3.5296    2.8405    1.6296   -0.4149;
                        4.1008    3.7800    3.0269    1.7778   -0.2913;
                        4.2139    3.8495    3.0761    1.8155   -0.2609];

EP3(:,:,2) = 1.0e+06 * [2.4255    2.6808    2.2051    1.1186   -0.8443;
                        3.6950    3.5158    2.8300    1.6211   -0.4221;
                        4.0924    3.7743    3.0225    1.7743   -0.2943;
                        4.2101    3.8469    3.0741    1.8139   -0.2623];

EP3(:,:,3) = 1.0e+06 * [2.3754    2.6474    2.1799    1.0982   -0.8615;
                        3.6767    3.5036    2.8207    1.6135   -0.4285;
                        4.0849    3.7693    3.0187    1.7712   -0.2969;
                        4.2068    3.8446    3.0724    1.8125   -0.2635];

EP3(:,:,4) = 1.0e+06 * [2.3301    2.6173    2.1571    1.0798   -0.8771;
                        3.6601    3.4925    2.8123    1.6067   -0.4343;
                        4.0781    3.7647    3.0152    1.7683   -0.2993;
                        4.2037    3.8426    3.0708    1.8112   -0.2646];

EP3(:,:,5) = 1.0e+06 * [2.2888    2.5899    2.1364    1.0630   -0.8913;
                        3.6450    3.4824    2.8046    1.6005   -0.4395;
                        4.0719    3.7606    3.0120    1.7658   -0.3015;
                        4.2009    3.8407    3.0694    1.8100   -0.2656];

% dimensions of matrix EP3: [N,k,r]

[Xgrid,Ygrid]=meshgrid(xV_vector,H_D_ratio);
EP3_grid = permute(EP3,[2 3 1]);
figure
hold on
for f=1:N
    surf(Xgrid,Ygrid,EP3_grid(:,:,f)'); %,'Color',col(:,:,f));
    legendInfo{f} = [num2str(Temp(f)-273.15) ' °C'];
end
xticks(xV_vector);
yticks(H_D_ratio);
title 'EP_3'
xlabel 'x_v (molar fraction of H_2 in V and R) [-]', ylabel 'H/D reactor ratio [-]'
zlabel('EP_3')
legend(legendInfo)
%s.EdgeColor='none';

[the cyclist]

MATLAB seems to have chosen a poor default view, which fails to illustrate the 3-D nature of the plot. Try adding

view(45,45)

after the plot, and you'll see something closer to what you expect.

[Francesco Guaresi]

Thank you very much! Imposing view(15,15) it works perfectly!

But is it possible to obtain the 4 surfaces in 4 different colors?

[the cyclist]

The surf command takes a fourth argument, for the color. You could write your loop in a way that uses a different color for each loop iteration.