draw line between points in the figure

    points_id={'p1','p2','p3','p4'}

    x=[100,120,130,140] %coordinates

    y=[200,220,330,340] %coordinates

    figure(1),scatter(x, y, 'b^');grid on;

    text(x, y, points_id)

    title('COORDINATE SYSTEM')

    xlabel('Y')

    ylabel('X')

% in this figure I wanna draw lines between points when user click on corresponding points.

[per isakson]

Search help for "line"

Answer 1

[Image Analyst]

Get the points, for example by using ginput. Then find out which of the points is closest to the 2 points they clicked on. Then draw a line between them. Here's a demo:

clc;
clear all;
workspace
points_id={'p1','p2','p3','p4'}
x=[100,120,130,140] %coordinates
y=[200,220,330,340] %coordinates
figure(1),scatter(x, y, 'b^');
grid on;
text(x, y, points_id)
title('COORDINATE SYSTEM')
xlabel('Y')
ylabel('X')
uiwait(msgbox('Click on two points', 'modal'));
[xu, yu] = ginput(2);
% Find the closest point to the first point where they clicked.
distances1 = sqrt((x-xu(1)).^2 + (y - yu(1)).^2)
[~, index1] = min(distances1)
% Find the closest point to the second point where they clicked.
distances2 = sqrt((x-xu(2)).^2 + (y - yu(2)).^2)
[~, index2] = min(distances2)
line([x(index1), x(index2)], [y(index1), y(index2)])

[sermet]

When I want to continue drawing after 2 points, for example I wanna create polygon by clicking on 4 points or more what should I do?

[Image Analyst]

Ask them in advance how many points they want to click on with inputdlg(). Then pass that number into ginput.

[sermet]

It is not known before, user decide it, it depends on the situation. What I want is users should be freely choose any points which they wanna draw polygon between them.

[Image Analyst]

Then use the mousedown or buttondown callback function of the axes to draw a line from the closest last point (the one they just clicked on) to the prior point.

[sermet]

could you give example codes for what you meant please?

[Image Analyst]

I don't have any sample/demo code for that. Either you or I would have to write it. I vote for you.