stream3 returns error: Sample points must be unique

Question

Florian G 2024-9-13

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2152720-stream3-returns-error-sample-points-must-be-unique

评论： dpb 2024-9-15

Hello, I searched the community forum and tried my best to resolve the issue myself, but I could not do it.

Here is my code:

clc; close; clear all;
format compact
%% Cylindrical Coordinates
% Generate cylindrical coordinates
phi = [0 pi/2 pi 3*pi/2];
rho = [0.25 2];
z = [1 2];
% Create a meshgrid for theta, r, and z
[Phi, Rho, Z] = meshgrid(phi, rho, z);
% Convert cylindrical coordinates to Cartesian coordinates
[X, Y, Z] = pol2cart(Phi, Rho, Z);
% Combine X, Y, Z into a single matrix
points = [X(:), Y(:), Z(:)];
% Find unique rows and their indices
[unique_points, ~, ~] = unique(points, 'rows');
% Check for duplicates (optional)
num_duplicates = size(points, 1) - size(unique_points, 1);
if num_duplicates > 0
    fprintf('There are %d duplicate points.\n', num_duplicates);
else
    fprintf('All points are unique.\n');
end
% Plot the points in 3D space (optional)
figure;
% plot3(X, Y, Z, 'o','DisplayName','Sample Points');
xlabel('X');
ylabel('Y');
zlabel('Z');
title('3D Cylindrical Coordinates');
grid on; axis equal; hold on;
%% Circular magnetic field
% Current in negative z-direction (negative values mean the current
% direction is in positive z-direction)
I = 1;
% Absolute Value of the cylindrical H-field at corresponding positions of
% the radius in phi-direction (all other components are zero)
Hc_phi = 1/(2*pi*Rho);
% Calculate the x-, y- and z-components of the cylindrical field
Hc_x = Hc_phi .* sin(Phi);
Hc_y = -Hc_phi .* cos(Phi);
Hc_z = zeros(size(Z));
% Draw the vector-arrows of the cylindrical field
quiver3(X,Y,Z,Hc_x,Hc_y,Hc_z,'AutoScale','off');
%% Longitudinal magnetic field
Hl = 0.4; % Absolute field strength (+ = neg. z-direction)
Hl_x = zeros(size(X));
Hl_y = zeros(size(Y));
Hl_z = -Hl .* ones(size(Z));
% Draw the vector-arrows of the longitudinal field
quiver3(X,Y,Z,Hl_x,Hl_y,Hl_z,'AutoScale','off');
%% Helical magnetic field (sum of cylindrical and longitudinal field)
H_x = Hc_x + Hl_x;
H_y = Hc_y + Hl_y;
H_z = Hc_z + Hl_z;
% Draw the vector arrows of the helical field
quiver3(X,Y,Z,H_x,H_y,H_z,'AutoScale','off','LineWidth',1.5)
% Draw the fieldlines of the helical field
[startX,startY,startZ] = meshgrid([-1 1],[-1 1],1);
% startpoints = [startX(:), startY(:), startZ(:)]; % unique, manually checked
% samplepoints = [X(:), Y(:), Z(:)]; % unique, manually checked
verts  = stream3(X,Y,Z,H_x,H_y,H_z,startX,startY,startZ); 
lineobj = streamline(verts);
view(3)

Sorry, it might be a bit overwhelming. Ultimately, I just want to get streamlines of H_x, H_y and H_z on the X, Y, Z grid. But I get the following output of the script:

All points are unique.
Error using matlab.internal.math.interp1
Sample points must be unique.
Error in interp1 (line 188)
VqLite = matlab.internal.math.interp1(X,V,method,method,Xqcol);
Error in stream3 (line 66)
syi=interp1(yy(:),1:szu(1),sy(k));
Error in test (line 62)
verts  = stream3(X,Y,Z,H_x,H_y,H_z,startX,startY,startZ); 

What is the Problem here? Is my check for unique points wrong?

Thank you very much in advance!

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Florian G 2024-9-15

编辑：Florian G 2024-9-15

Thank you for the input! :)

This actually helped me solve my problem. In my revised script i basically just replaced this:

% Generate cylindrical coordinates

phi = [0 pi/2 pi 3*pi/2];

rho = [0.25 2];

z = [1 2];

% Create a meshgrid for theta, r, and z

[Phi, Rho, Z] = meshgrid(phi, rho, z);

% Convert cylindrical coordinates to Cartesian coordinates

[X, Y, Z] = pol2cart(Phi, Rho, Z);

With this:

% Generate cartesian coordinates

x = -5.025:0.05:5.025;

y = x;

z = 0:0.25:10;

% Create a meshgrid for x, y, and z

[X, Y, Z] = meshgrid(x, y, z);

% Convert cylindrical coordinates to Cartesian coordinates

[Phi, Rho, Z] = cart2pol(X, Y, Z);

To get the following working example:

clc; close; clear all;

format compact

%% Cartesian Coordinates

% Generate cylindrical coordinates

x = -5.025:0.05:5.025;

y = x;

z = 0:0.25:10;

% Create a meshgrid for x, y, and z

[X, Y, Z] = meshgrid(x, y, z);

% Convert cylindrical coordinates to Cartesian coordinates

[Phi, Rho, Z] = cart2pol(X, Y, Z);

% Combine X, Y, Z into a single matrix

points = [X(:), Y(:), Z(:)];

% Find unique rows and their indices (optional)

[unique_points, ~, ~] = unique(points, 'rows');

% Check for duplicates (optional)

num_duplicates = size(points, 1) - size(unique_points, 1);

if num_duplicates > 0

fprintf('There are %d duplicate points.\n', num_duplicates);

else

fprintf('All points are unique.\n');

end

% Configure 3D plot

figure;

% plot3(X, Y, Z, 'o','DisplayName','Sample Points'); % optionally plot points

xlabel('X');

ylabel('Y');

zlabel('Z');

title('3D Cylindrical Coordinates');

grid on; axis equal; hold on;

%% Circular magnetic field

% Current in negative z-direction (negative values mean the current

% direction is in positive z-direction)

I = 1;

% Absolute Value of the cylindrical H-field at corresponding positions of

% the radius in phi-direction (all other components are zero)

Hc_phi = 1/(2*pi*Rho);

% Calculate the x-, y- and z-components of the cylindrical field

Hc_x = Hc_phi .* sin(Phi);

Hc_y = -Hc_phi .* cos(Phi);

Hc_z = zeros(size(Z));

% % Draw the vector-arrows of the cylindrical field

% quiver3(X,Y,Z,Hc_x,Hc_y,Hc_z,'AutoScale','off');

%% Longitudinal magnetic field

Hl = 0.4; % Absolute field strength (+ = neg. z-direction)

Hl_x = zeros(size(X));

Hl_y = zeros(size(Y));

Hl_z = -Hl .* ones(size(Z));

% % Draw the vector-arrows of the longitudinal field

% quiver3(X,Y,Z,Hl_x,Hl_y,Hl_z,'AutoScale','off');

%% Helical magnetic field (sum of cylindrical and longitudinal field)

H_x = Hc_x + Hl_x;

H_y = Hc_y + Hl_y;

H_z = Hc_z + Hl_z;

% % Draw the vector arrows of the helical field

% quiver3(X,Y,Z,H_x,H_y,H_z,'AutoScale','off','LineWidth',1.5)

% Draw the fieldlines of the helical field

[startX,startY,startZ] = meshgrid([-0.25 0.25],[-0.25 0.25],10);

% startpoints = [startX(:), startY(:), startZ(:)]; % unique, manually checked

% samplepoints = [X(:), Y(:), Z(:)]; % unique, manually checked

verts = stream3(X,Y,Z,H_x,H_y,H_z,startX,startY,startZ,[1e-2 1e5]);

lineobj = streamline(verts);

view(3)

dpb 2024-9-15

I knew the above would run; wasn't sure it would produce the grid you wished, however...

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stream3 returns error: Sample points must be unique

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stream3 returns error: Sample points must be unique

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3 个评论
显示 1更早的评论隐藏 1更早的评论