Filtering data from interpolated points on patch

Question

Kovacs Mario 2024-3-11

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2093011-filtering-data-from-interpolated-points-on-patch

评论： Voss 2024-3-11

采纳的回答： Voss

在 MATLAB Online 中打开

Hi,

The problem would be:

In the figure below, there are 6 points (xy) and the values (q) are assigned to these points. From these points, 3 triangles, colored by value, are drawn using the PATCH command.

By interpolating along two vertical lines I have determined 10-10 values. However, my problem is that it also interpolates values to places where there is no colored triangle (only white background).

Is there any way to zero out all the interpolated values that do not fall on the colored areas?

(This just demonstrates a simpler scenario, there are where I need to filter out these points for a model with many more triangles and white areas.)

The programme can be found below.

FIGURE:

PROGRAM:

xy = [1 3.1
    2.6 2.8
    1.3 1.9
    2.8 1.5
    3.7 2.1
    2 0.9];
Connectivity_matrix = [3 2 1
    5 2 4
    6 4 3];
q = [1 2 3 1 2 3]';
RGB = [0 0 1
    0 0.5 1
    0 1 1
    0 1 0.5
    0 1 0
    0.5 1 0
    1 1 0
    1 0.5 0
    1 0 0];
I = scatteredInterpolant(xy,q);
[x,y] = meshgrid([1.7; 2.4],linspace(0.8,3.2,10));
v = I(x,y)
figure ()
set(gcf, 'color', 'w')
colormap(RGB);
colorbar('EastOutside')
patch('Faces',Connectivity_matrix,'Vertices', xy,'FaceVertexCData',q,'FaceColor','interp')
axis equal
str = compose('%.3f  ',v);
text(x(:),y(:),str(:),'HorizontalAlignment','right','BackgroundColor','w')
line(x(:),y(:),'LineStyle','none','Marker','o','Color',[0.75 0 0.75],'MarkerFaceColor',[0.75 0 0.75])

Do you have any idea how can I solve this problem?

Thank you so much for your helpful comments!

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Answer 1

Voss 2024-3-11

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2093011-filtering-data-from-interpolated-points-on-patch#answer_1423681

在 MATLAB Online 中打开

xy = [1 3.1

2.6 2.8

1.3 1.9

2.8 1.5

3.7 2.1

2 0.9];

Connectivity_matrix = [3 2 1

5 2 4

6 4 3];

q = [1 2 3 1 2 3]';

RGB = [0 0 1

0 0.5 1

0 1 1

0 1 0.5

0 1 0

0.5 1 0

1 1 0

1 0.5 0

1 0 0];

I = scatteredInterpolant(xy,q);

[x,y] = meshgrid([1.7; 2.4],linspace(0.8,3.2,10));

v = I(x,y)

v = 10×2

3.5931 2.8530 3.2777 2.7888 2.9945 1.8470 2.6885 1.5410 2.5098 1.6863 2.6667 1.8431 2.3388 2.0000 1.9162 2.1457 1.4936 1.8717 1.2417 1.8429

% use inpolygon to say which points are in each triangle:

N_triangles = size(Connectivity_matrix,1);

in_triangle = false(numel(x),N_triangles);

for ii = 1:N_triangles

tri_xy = xy(Connectivity_matrix(ii,:),:);

in_triangle(:,ii) = inpolygon(x(:),y(:),tri_xy(:,1),tri_xy(:,2));

end

% a point is in a triangle if it is in any triangle:

in_triangle = any(in_triangle,2);

% zero out the interpolated values of points not in a triangle:

v(~in_triangle) = 0

v = 10×2

0 0 0 0 2.9945 1.8470 2.6885 1.5410 0 0 0 0 2.3388 0 1.9162 2.1457 1.4936 0 0 0

figure ()

set(gcf, 'color', 'w')

colormap(RGB);

colorbar('EastOutside')

patch('Faces',Connectivity_matrix,'Vertices', xy,'FaceVertexCData',q,'FaceColor','interp')

axis equal

str = compose('%.3f ',v);

% text(x(:),y(:),str(:),'HorizontalAlignment','right','BackgroundColor','w')

% line(x(:),y(:),'LineStyle','none','Marker','o','Color',[0.75 0 0.75],'MarkerFaceColor',[0.75 0 0.75])

% make texts and dots only at points in a triangle:

text(x(in_triangle),y(in_triangle),str(in_triangle),'HorizontalAlignment','right','BackgroundColor','w')

line(x(in_triangle),y(in_triangle),'LineStyle','none','Marker','o','Color',[0.75 0 0.75],'MarkerFaceColor',[0.75 0 0.75])

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Kovacs Mario 2024-3-11

编辑：Voss 2024-3-11

在 MATLAB Online 中打开

Thank you so much for your answer!

Maybe you can help me, if there are not only triangles but also quadrilaterals in the model, how should I modify your program?

You can see the program for that below:

xy = [1 3.1
    2.6 2.8
    1.3 1.9
    2.8 1.5
    3.7 2.1
    2 0.9
    3 4];
Connectivity_matrix_tria = [5 2 4
    6 4 3];
Connectivity_matrix_quad = [3 2 7 1];
q = [1 2 3 1 2 3 3]';
RGB = [0 0 1
    0 0.5 1
    0 1 1
    0 1 0.5
    0 1 0
    0.5 1 0
    1 1 0
    1 0.5 0
    1 0 0];
I = scatteredInterpolant(xy,q);
[x,y] = meshgrid([1.7; 2.4],linspace(0.8,4,10));
v = I(x,y)
figure ()
set(gcf, 'color', 'w')
colormap(RGB);
colorbar('EastOutside')
patch('Faces',Connectivity_matrix_tria,'Vertices', xy,'FaceVertexCData',q,'FaceColor','interp')
patch('Faces',Connectivity_matrix_quad,'Vertices', xy,'FaceVertexCData',q,'FaceColor','interp')
axis equal
str = compose('%.3f  ',v);
text(x(:),y(:),str(:),'HorizontalAlignment','right','BackgroundColor','w')
line(x(:),y(:),'LineStyle','none','Marker','o','Color',[0.75 0 0.75],'MarkerFaceColor',[0.75 0 0.75])

Thank you so much for your help! :)

Voss 2024-3-11

在 MATLAB Online 中打开

You're welcome!

It works pretty much the same way, since inpolygon will work for any polygon.

xy = [1 3.1

2.6 2.8

1.3 1.9

2.8 1.5

3.7 2.1

2 0.9

3 4];

Connectivity_matrix_tria = [5 2 4

6 4 3];

Connectivity_matrix_quad = [3 2 7 1];

q = [1 2 3 1 2 3 3]';

RGB = [0 0 1

0 0.5 1

0 1 1

0 1 0.5

0 1 0

0.5 1 0

1 1 0

1 0.5 0

1 0 0];

I = scatteredInterpolant(xy,q);

[x,y] = meshgrid([1.7; 2.4],linspace(0.8,4,10));

v = I(x,y)

v = 10×2

3.5931 2.8539 3.1799 2.7702 2.7905 1.6430 2.5098 1.6863 2.6205 1.8954 2.0571 2.1046 1.4936 1.9314 1.6258 2.1405 1.6156 2.3497 1.5517 2.4667

% use inpolygon to say which points are in each polygon:

C = {Connectivity_matrix_tria; Connectivity_matrix_quad};

NC = numel(C);

N_poly = cellfun(@(x)size(x,1),C);

in_poly = cell(1,NC);

NX = numel(x);

for ii = 1:NC

in_poly{ii} = false(NX,N_poly(ii));

for jj = 1:N_poly(ii)

poly_xy = xy(C{ii}(jj,:),:);

in_poly{ii}(:,jj) = inpolygon(x(:),y(:),poly_xy(:,1),poly_xy(:,2));

end

% a point is in a polygon if it is in any polygon:

in_poly = any([in_poly{:}],2);

% zero out the interpolated values of points not in a triangle:

v(~in_poly) = 0

v = 10×2

0 0 0 0 2.7905 1.6430 0 0 2.6205 0 2.0571 0 1.4936 1.9314 1.6258 2.1405 0 2.3497 0 0

figure ()

set(gcf, 'color', 'w')

colormap(RGB);

colorbar('EastOutside')

patch('Faces',Connectivity_matrix_tria,'Vertices', xy,'FaceVertexCData',q,'FaceColor','interp')

patch('Faces',Connectivity_matrix_quad,'Vertices', xy,'FaceVertexCData',q,'FaceColor','interp')

axis equal

str = compose('%.3f ',v);

% text(x(:),y(:),str(:),'HorizontalAlignment','right','BackgroundColor','w')

% line(x(:),y(:),'LineStyle','none','Marker','o','Color',[0.75 0 0.75],'MarkerFaceColor',[0.75 0 0.75])

text(x(in_poly),y(in_poly),str(in_poly),'HorizontalAlignment','right','BackgroundColor','w')

line(x(in_poly),y(in_poly),'LineStyle','none','Marker','o','Color',[0.75 0 0.75],'MarkerFaceColor',[0.75 0 0.75])

Kovacs Mario 2024-3-11

Thank you!

Voss 2024-3-11

You're welcome!

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Filtering data from interpolated points on patch

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Filtering data from interpolated points on patch

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