Points inside multiple polygon for contour
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I made the following contourplot.
Then, I plot discretized points over this plot.
I wanted to find the (x,y) coordinates of the discretized points within the region between the boundaries 40.94 and 43. This is the way how I approached it. With contourtable I acquired the (x,y) coordinates of the contourlines.
muSP = [0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9];
muRP = [0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9];
[X,Y] = meshgrid(muSP,muRP);
Z = cell2mat(reshape(AoR_mean,[9,9]));
[C,h] = contour(X,Y,Z,(40.9431:2.0538:42.9969));
hold on
title('Angle of Repose - Ledge Test 2D');
xlabel('\mu_s')
ylabel('\mu_r')
clabel(C,h,'LabelSpacing',500,'FontSize',8);
h.LevelList = round(h.LevelList,2);
set(gca,'XTick',0.1:0.1:0.9,'XTickLabel',0.1:0.1:0.9,'XTickLabelRotation',45);
set(gca,'YTick',0.1:0.1:0.9,'YTickLabel',0.1:0.1:0.9);
grid on
% Extract x- and y-coordinates of contour lines
contourTable = getContourLineCoordinates(h);
% Define grid for the variable space
N1 = 80;
muRP_grid = linspace(0.1,0.9,N1);
muSP_grid = linspace(0.1,0.9,N1);
[R,S] = meshgrid(muRP_grid,muSP_grid);
plot(R,S,'.r');
hold off
% x- and y-coordinates of polygon vertices, i.e. between AoR of 40.11 degrees
% and AoR of 43.83 degrees
xv = table2array(contourTable(1:31,3));
yv = table2array(contourTable(1:31,4));
inside_variablespace = inpolygon(R,S,xv,yv);
% x- and y-coordinates corresponding to the discretized points in the
% variable spac
xcoord = R(inside_variablespace);
ycoord = S(inside_variablespace);
However, for some reason I don't get de discretized points within the boundaries 40.94 and 43.
采纳的回答
KSSV
2020-9-29
0 个投票
Read about inpolygon. If you have a polygon and a set of points, you cann extract the points lying inside this polygon using that.
8 个评论
Tessa Kol
2020-9-29
I did read about inpolygon and tried the solution with NaN. Didn't work.
Also I used the (x,y) coordinates of the contourlines. I obtained these coordinates with the function getContourLineCoordinates.
Since that didn't work either, what can be the problem?
Tessa Kol
2020-9-29
I think I know where is goes wrong.
Matlab connects two boundary lines that shouldn't be connected. Hence the problem.
KSSV
2020-9-29
You remove the boundary line..
Tessa Kol
2020-9-29
Tessa, the polygon is defined by the (x,y) values within level 40.94, only.
idx = contourTable.Level==40.94; % or contourTable.Group==1
inpolygon(x,y,contourTable.X(idx), contourTable.Y(idx))
Tessa Kol
2020-9-29
Check out the examples in the documentation
You can call inpolygon on the outer polygon, then call inpolygon on the inner polygon, then remove selected points that are in both.
Example
A = inpolygon(...)
B = inpolygon(...)
A(B) = false;
Use these answers as a stepping stone rather than looking for full solutions.
Tessa Kol
2020-9-29
It worked thank you! I adjusted the code as follow:
xv1 = [0.9;table2array(contourTable(1:15,3));0.9];
yv1 = [0.9;table2array(contourTable(1:15,4));0.9];
xv2 = table2array(contourTable(16:18,3));
yv2 = table2array(contourTable(16:18,4));
xv3 = table2array(contourTable(19:31,3));
yv3 = table2array(contourTable(19:31,4));
inside_variablespace1 = inpolygon(R,S,xv1,yv1);
inside_variablespace2 = inpolygon(R,S,xv2,yv2);
inside_variablespace3 = inpolygon(R,S,xv3,yv3);
% x- and y-coordinates corresponding to the discretized points in the
% variable spac
inside_variablespace1(inside_variablespace2) = false;
inside_variablespace1(inside_variablespace3) = false;
xcoord = R(inside_variablespace1);
ycoord = S(inside_variablespace1);
Resulting in:
更多回答（1 个）
Ameer Hamza
2020-9-29
There is no need to use inpolygon here. You can directly create a mask from the Z matrix. Following shows an example, and find the x and y coordinates from the mesh between contour lines at 0.33 and 0.66
[X, Y] = meshgrid(linspace(-1, 1));
Z = X.^2 + Y.^2;
levels = [0 0.33 0.66 1]; % levels for contour plot
mask = Z < 0.66 & Z > 0.33;
x_coord = X(mask);
y_coord = Y(mask);
contour(X, Y, Z, levels)
hold on
plot(x_coord, y_coord, '+')
4 个评论
Tessa Kol
2020-9-29
Ameer Hamza
2020-9-29
You will write it like this
mask = Z < 43 & Z > 40.97;
x_coord = X(mask);
y_coord = Y(mask);
The x-y coordinates will be extracted from corresponding locations in X and Y matrix.
Tessa Kol
2020-9-29
Ameer Hamza
2020-9-29
What is the error. In the data you shared, AoR_mean is undefined, so I cannot run your code to see the issue.
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