How to plot graph using ginput?

Hi friends i want to plot a graph between two graphic input, i did it but i want to make it as my input should be visible before plotting.

This is my code..

axis([0 100 0 100]);

hold on

nodes = 2;

PauseTime = 0.05; 

[x,y] = ginput(nodes);

plot(x,y,'--ys','LineWidth',2,'MarkerEdgeColor','b','MarkerFaceColor','b', 'MarkerSize',4);

please help me....

Answer 1

[OCDER]

To do what you want would require using callback functions. See this video here to understand how it works: https://blogs.mathworks.com/videos/2008/05/27/advanced-matlab-capture-mouse-movement/

To summon this function, do:

plotLines(5) %for 5 points, 4 lines

The function is below. You have to modify this based on what you want to accomplish with drawing lines. Play around with the callback functions: startLine, stopLine, dragLine.

function plotLines(nodes)
axis([0 100 0 100]);
set(gca, 'xlim', [0 100], 'ylim', [0 100]);
hold on;
%nodes = 2; %It's now the function input
PauseTime = 0.05; %You can use drawnow instead of pause to refresh plots.
set(gcf, 'WindowButtonDownFcn', @startLine);
set(gcf, 'WindowButtonUpFcn', @stopLine);

      function startLine(varargin)
          pt = get(gca, 'currentpoint');
          if isempty(findobj(gca, 'type', 'line'))
              plot(gca, [pt(1,1), pt(1,1)], [pt(1,2), pt(1,2)], '--ys', 'LineWidth',2, 'MarkerEdgeColor','b', 'MarkerFaceColor','b', 'MarkerSize',4);
          else
              Lx = findobj(gca, 'type', 'line');
              Xdata = get(Lx, 'Xdata');
              Ydata = get(Lx, 'Ydata');
              if length(Xdata) > nodes-1; return; end %Edit this depending on your definition of "node".
              Xdata(end+1) = pt(1,1);
              Ydata(end+1) = pt(1,2);
              set(Lx, 'Xdata', Xdata, 'Ydata', Ydata);   
          end
          set(gcf, 'WindowButtonMotion', @dragLine)
      end

      function dragLine(varargin)
          pt = get(gca, 'currentpoint');
          Lx = findobj(gca, 'type', 'line');
          Xdata = get(Lx, 'Xdata');
          Ydata = get(Lx, 'Ydata');
          Xdata(end) = pt(1,1);
          Ydata(end) = pt(1,2);
          set(Lx, 'Xdata', Xdata, 'Ydata', Ydata);
      end

      function stopLine(varargin)
          set(gcf, 'WindowButtonMotion', '');
      end
  end

[VALARMATHY K]

sorry i don't want to do this with call back, i just what i want is, if select two points in my graph, after plot i am getting a stright line between that two points (two blue dots), i want that when i click cursor one blue dot shoud be shown on my graph..

This is my output when i click 1st point

This is output after 2nd click because i assigned only 2 nodes..

[OCDER]

Have you tried the callback solution? The other way to do this is to use multiple ginputs. 1st ginput - draw the 1st point only. 2nd ginput - draw the 2nd point and the line.

axis([0 100 0 100]);
hold on
nodes = 2;
PauseTime = 0.05;

[x,y] = ginput(1);
Lx = plot(x,y,'--ys','LineWidth',2,'MarkerEdgeColor','b','MarkerFaceColor','b', 'MarkerSize',4);

for k = 1:nodes-1
    [x,y] = ginput(1);
    Lx.XData = [x, Lx.XData];
    Lx.YData = [y, Lx.YData];
end

[VALARMATHY K]

when i run this code i am getting this error....

[OCDER]

Hm, that's odd. Do you have an older version of Matlab? Try this instead:

clear
close all
clc

axis([0 100 0 100]);
hold on
nodes = 2;
PauseTime = 0.05;
[x,y] = ginput(1);
Lx = plot(x,y,'--ys','LineWidth',2,'MarkerEdgeColor','b','MarkerFaceColor','b', 'MarkerSize',4);
for k = 1:nodes-1
    [x,y] = ginput(1);
    XData = get(Lx, 'XData');
    YData = get(Lx, 'YData');
    set(Lx, 'Xdata', [x, XData], 'YData', [y, YData]);
end

[VALARMATHY K]

Thank you sir its working

Answer 2

[Walter Roberson]

Consider using imline()

[VALARMATHY K]

Thank you for your answer, sorry i don't know where i have to put that command (imline())...

[Walter Roberson]

Instead of using ginput() to get the coordinates, you could imline(), which allows the user to place a draggable resizable line -- so they could effectively select points and move the selection around and see the change in the line, without you having to program in the behaviours yourself.

[VALARMATHY K]

Thank you sir