MATLAB: Draw line between points in the figure

linescatter

    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.

Best Answer

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)])

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Try this:

Array = linspace(0, 2*pi, 200);
x = cos(Array);
y = sin(Array);
plot(x,y, 'bo-')
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 
promptMessage = sprintf('Click two points,\nor Cancel to abort processing?');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
  return;
end
[twoPointsX, twoPointsY] = ginput(2)
hold on;
plot(twoPointsX,twoPointsY, 'rd')
% Find the point closest to the first clicked point.
distances = sqrt((x - twoPointsX(1)) .^2 + (y - twoPointsY(1)) .^ 2)
[minDistance1, index1] = min(distances)
% Find the point closest to the Second clicked point.
distances = sqrt((x - twoPointsX(2)) .^2 + (y - twoPointsY(2)) .^ 2)
[minDistance2, index2] = min(distances)
% Plot the points on the circumference in red squares.
plot([x(index1), x(index2)], [y(index1), y(index2)], 'rs-')
% Calculate the final distance:
distance = sqrt( (x(index1)-x(index2))^2 + (y(index1)-y(index2))^2)
message = sprintf('The distance = %f', distance);
uiwait(helpdlg(message));

Best Answer

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MATLAB: How can I seperate between points id and scatter markers in figure

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