Store values generate in a function call in an array

Question

Nnamdi Chukwunenye 2020-9-2

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/588106-store-values-generate-in-a-function-call-in-an-array

编辑： Bruno Luong 2020-9-3

Hi I am trying to store the coordinates of the 4 spheres I am plotting from a function call. I can only return the final spheres coordinates instead of all of them. Any help would be greatly appreciated.

xyz = [-8.67212090030965	-7.78294481282592	4.19809966191787
4.30363429770975	-6.33796132936349	2.30412196271579
11.4626419696253	3.31049523749869	2.84193335035400
1.28757516363600	6.20802478748340	11.1358580308193];
x1 = xyz(:, 1);
y1 = xyz(:, 2);
z1 = xyz(:, 3); 
SizeXYZ = size(xyz,1);
for i = 1:SizeXYZ
  [x,y,z spheresXYZ] = createspheres(x1(i),y1(i),z1(i));
  surf(x,y,z,'FaceColor', 'k');
  hold on
end
%
function [X,Y,Z, spheresXYZ] =createspheres(spherex, spherey, spherez)
[x, y, z] = sphere(4);
X = x+spherex;
Y = y+spherey;
Z = z+spherez;
spheresXYZ = [X,Y,Z];
end

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Rik 2020-9-2

I'm not sure I understand what you mean. Could you provide an example of what you want as the output?

Nnamdi Chukwunenye 2020-9-2

Hi, Rik so the code is generates 4 spheres, and I want an array (preferably a matrix, but from my attempts it might need to be a cell array) that contains all the coordinates of the 4 spheres.

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Answer 1

Bruno Luong 2020-9-2

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https://ww2.mathworks.cn/matlabcentral/answers/588106-store-values-generate-in-a-function-call-in-an-array#answer_488803

编辑：Bruno Luong 2020-9-2

在 MATLAB Online 中打开

spheresXYZ = cell(1,SizeXYZ);
for i = 1:SizeXYZ 
  [x,y,z spheresXYZ{i}] = createspheres(x1(i),y1(i),z1(i));
  ...
end

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Nnamdi Chukwunenye 2020-9-2

Hey Bruno, why does the spheresXYZ have to be a cell array instead of a matrix?

Bruno Luong 2020-9-3

编辑：Bruno Luong 2020-9-3

在 MATLAB Online 中打开

If you prefer storage 3D array (assuming the function returns always a fixed size output) you can get them like this at the end of the loop

spheresXYZ = cell(1,SizeXYZ);
for i = 1:SizeXYZ 
  ...
end
spheresXYZ = cat(3, spheresXYZ{:});

Then when needed, each sphere #k coordinates can be obtained by

spheresXYZ(:,:,k)

There is a whole bunch of techniques to preallocate nd array (see e.g. Rik's answer) that can be adapted for each case. This topic is beyond this thread.

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Answer 2

Rik 2020-9-3

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https://ww2.mathworks.cn/matlabcentral/answers/588106-store-values-generate-in-a-function-call-in-an-array#answer_488989

在 MATLAB Online 中打开

Instead of using a cell array, you can also use a 3D matrix:

[~,~,~,spheresXYZ]=createspheres(0,0,0);spheresXYZ(1,1,SizeXYZ)=0;
for n = 1:SizeXYZ
  [x,y,z,spheresXYZ(:,:,n)] = createspheres(x1(n),y1(n),z1(n));
end