How to show selected points and connect first point to last point?

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Mariam Shahab 2022-9-26

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https://ww2.mathworks.cn/matlabcentral/answers/1812505-how-to-show-selected-points-and-connect-first-point-to-last-point

评论： Mariam Shahab 2022-10-1

采纳的回答： Daksh

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Hi all,

I have the following code:

[x,y]=ginput(); % user can chose any number of coordinates by clicking on graph
plot(x,y);

Is there a way that when the user clicks in the graph, the selected points are marked (to show the selected points)?

Lastly, I want the first point to connect to the last point, but I am not sure how to do this.

I will appreaciate if someone can help me out with my two inquiries. Many thanks!

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Geoff Hayes 2022-9-26

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@Mariam Shahab - if you want the last point to be connected to the first point, then the easiest way to do this might be to append the first points' x and y coordinates to the x and y arrays respectively. To show which points, have been selected, just change the call to plot so that you incoude a shape at that point. For example

plot([x ; x(1)],[y ; y(1)], 'bo-');

might do what you want.

Mariam Shahab 2022-9-26

Thank you. This was what I was looking for.

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Answer 1

Daksh 2022-9-29

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Hi

It is my understanding that you wish to view marked points in real time as the user selects multiple points in a plot using "ginput" and you want all points connected, all the way from the first to the last in order through a line.

The following code illustatres how to achieve the same; I've assumed you know the number of points to be marked beforehand (I've taken 5 points in this case) and I've also put the number tag string on each marked point to depict the order of point marking:

clear all
close all
%assuming you want to plot 5 points for example
n=5;
a=zeros(n,1);
b=zeros(n,1);
%running a loop over all selected points
for i=1:5
    %allowing user to click a point to choose, x,y store the coordinates
    [x,y] = ginput(1);
    %text depiction for each point, with "i" as the point marker
    h1 = text(x,y,int2str(i), ...
                'HorizontalAlignment','center', ...
                'Color', [1 0 0], ...
                'FontSize',8);
    a(i)=x;
    b(i)=y;
end
hold on
%plotting a line between all points
plot([a ; a(1)],[b ; b(1)], 'b-');
hold off