how to get one shape out of multiple shapes

Question

Asliddin Komilov 2023-12-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2060069-how-to-get-one-shape-out-of-multiple-shapes

评论： Asliddin Komilov 2023-12-22

Hi,

I have multiple shapes I need to merge into a single shape, because I have sets of shapes those I have to merge and compare with each other (put into a one plot).

the set of data is attached and I can plot it like this:

plot(X(:, [1:end 1])', Y(:, [1:end 1])')

let me know, if you know how to do it, thanks.

I got this shape using patch, but it generated a Patch file that I cannot use.

Ideally, I would like my data was interpolated so the final shape will not have sharp edges but be smooth and go down to Y=0.

Help me handle that too if you can. thanks

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Dyuman Joshi 2023-12-13

"I got this shape using patch, but it generated a Patch file that I cannot use."

You can't use the patch object or you can't use the output generated?

What is the expected output? It will be helpful if you can show an illustration.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

DGM 2023-12-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2060069-how-to-get-one-shape-out-of-multiple-shapes#answer_1370904

在 MATLAB Online 中打开

data.mat

patch() doesn't create a file. If you created a file somehow, nobody knows how you did it.

I'm not sure where this is going, but here's a guess.

% loads X,Y

load data.mat

% get rid of NaNs

xhasnans = any(isnan(X),2);

yhasnans = any(isnan(Y),2);

goodrows = ~(xhasnans | yhasnans);

X = X(goodrows,:);

Y = Y(goodrows,:);

% find convex hull

K = convhull(double(X),double(Y));

Xh = X(K);

Yh = Y(K);

% plot the convex hull, show the curve endpoint

plot(Xh,Yh); hold on

plot(X(1),Yh(1),'o')

% get rid of the base of the curve

Xh = Xh(3:end-1);

Yh = Yh(3:end-1);

% extrapolate to Y=0 from last 10 datapoints

Np = 10; % number of points to use

% the right-hand part of the curve

Yhr = Yh(1:Np);

Xhr = Xh(1:Np);

Yexr = [0;Yhr];

Xexr = interp1(Yhr,Xhr,Yexr,'linear','extrap');

% the left-hand part of the curve

Yhl = Yh(end-Np+1:end);

Xhl = Xh(end-Np+1:end);

Yexl = [Yhl;0];

Xexl = interp1(Yhl,Xhl,Yexl,'linear','extrap');

% put them back together

Xex = [Xexr; Xh(Np+1:end-Np); Xexl];

Yex = [Yexr; Yh(Np+1:end-Np); Yexl];

% close the curve (if needed

Xex = Xex([1:end 1]);

Yex = Yex([1:end 1]);

% plot the extraploated curve, show the endpoint

plot(Xex,Yex,'--')

plot(Xex(1),Yex(1),'*')

3 个评论
显示 1更早的评论隐藏 1更早的评论

DGM 2023-12-14

I wouldn't call it a guess. I picked it manually based on the given hull. For a different set of polygons, I don't know that it would be consistently correct.

Asliddin Komilov 2023-12-15

data.mat

it didn't work korrektly for this set of data

请先登录，再进行评论。

Answer 2

Mathieu NOE 2023-12-13

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2060069-how-to-get-one-shape-out-of-multiple-shapes#answer_1370944

在 MATLAB Online 中打开

hello

try this

x = double(X(:));
y = double(Y(:));
% remove nan
id = isnan(x) & isnan(y);
x(id) = [];
y(id) = [];
% k = boundary(___,s) specifies shrink factor s using any of the previous syntaxes.
% s is a scalar between 0 and 1. Setting s to 0 gives the convex hull,
% and setting s to 1 gives a compact boundary that envelops the points.
% The default shrink factor is 0.5.
s = 0.1;
k = boundary(x,y,s);
x_out = x(k);
y_out = y(k);
% find lower left "corner" point to make extrapolation towards Y = 0
[mx,ix1] = min(x_out);
my = y_out(ix1);
ind = find(x_out<(mx+1));
slope = mean(diff(y_out(ind))./diff(x_out(ind)));
x_lower_left = mx - my/slope;
% find lower right "corner" point to make extrapolation towards Y = 0
[mx,ix2] = max(x_out);
my = y_out(ix2);
ind = find(x_out>(mx-1));
slope = mean(diff(y_out(ind))./diff(x_out(ind)));
x_lower_right = mx - my/slope;
% add those two new points to x_out and y_out
x_out2 = [x_out(1:ix2-1); x_lower_right; x_out(ix2:ix1); x_lower_left; x_out(ix1+1:end) ]  ;
y_out2 = [y_out(1:ix2-1); 0            ; y_out(ix2:ix1); 0           ; y_out(ix1+1:end) ]  ;
plot(x,y, '*', x_out, y_out, '-*r', x_out2, y_out2, '-g')

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 3

Asliddin Komilov 2023-12-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2060069-how-to-get-one-shape-out-of-multiple-shapes#answer_1372537

data.mat

thanks, but it didn't work correctly for this set of data.

7 个评论
显示 5更早的评论隐藏 5更早的评论

Asliddin Komilov 2023-12-20

编辑：Asliddin Komilov 2023-12-20

Sorry for the inconvinience, I am myself just recognizing the issues.

Extrapolation is not needed when max([y]) is at max([x]).

Asliddin Komilov 2023-12-22

在 MATLAB Online 中打开

I think it will work if the 2 halves of the data are treated separately as follows, but I don't know how to join them together and get read of common point.

cutxr=X(1:size(X)/2,:);
cutyr=Y(1:size(Y)/2,:);
cutxl=X(size(X)/2:end,:);
cutyl=Y(size(Y)/2:end,:);
% plot(cutxl(:, [1:end 1])', cutyl(:, [1:end 1])'); hold on
% plot(cutxr(:, [1:end 1])', cutyr(:, [1:end 1])')
% find convex hull
Kr = boundary(double(cutxr(:)),double(cutyr(:)),1);
Kl = boundary(double(cutxl(:)),double(cutyl(:)),1);
Xhr = cutxr(Kr);
Yhr = cutyr(Kr);
Xhl = cutxl(Kl);
Yhl = cutyl(Kl);
% plot the convex hull, show the curve endpoint
plot(Xhr,Yhr); hold on
plot(Xhl,Yhl)

请先登录，再进行评论。