Trace the Position of Cursor without Click

It works like GINPUT provided by MATLAB,but traces the position of cursor without click ...

Description

function [x,y]=gpos(h_axes)
%GPOS Get current position of cusor and return its coordinates in axes with handle h_axes
% h_axes - handle of specified axes
% [x,y] - cursor coordinates in axes h_aexs
%
% -------------------------------------------------------------------------
% Note:
% 1. This function should be called in the figure callback WindowButtonMotionFcn.
% 2. It works like GINPUT provided by Matlab,but it traces the position
% of cursor without click and is designed for 2-D axes.
% 3. It can also work even the units of figure and axes are inconsistent,
% or the direction of axes is reversed.
% -------------------------------------------------------------------------

• MATLAB release: MATLAB 6.5 (R13)

[drew slusser]

 

[Jasper Menger]

Nicely done!

Perhaps needless to say, but the function also works fine when called through a 'DownButtonFcn' callback.

[Dietrich Lueerssen]

The function is very useful (for me at least), and exactly what I wanted.

I discovered something in the code that may be an inadvertent mistake that only is important when the 'Dir' property of the x-axis is not set to 'normal'.

I am including here the original code as well as the fix (it replaces lines 45-46 in the original posting).

    % the following lines are the original code obtained from MATLAB
    % Central on 8 March 2006
% left_origin = pos_axes_unitfig(1) + width_axes_unitfig;
% x_cursor2origin_unitfig = -( pos_cursor_unitfig(1) - left_origin_unitfig );
    % this correction was proposed in order to avoid a possibly not
    % initialised (and in addition, an unused) variable
    % Dietrich Lueerssen
    left_origin_unitfig = pos_axes_unitfig(1) + width_axes_unitfig;
    x_cursor2origin_unitfig = -( pos_cursor_unitfig(1) - left_origin_unitfig );

[c Zhao]

easy to use

[Frank Pezzullo]

HI ... can i have an example code to run your function ... I try with my example but doesn't work. Thanks

My Example is:

t = (0:0.05:1)';
d1 = sin(2*pi*t)*[1 2 3];
d2 = cos(2*pi*t)*[1 2 3];
h=plot(t,[d1 d2]);
gpos(h)
set(h,'WindowButtonMotionFcn',@gpos)

[Tuss P.]

Brilliant m file, Zhao. Thank you very much for sharing this with us. I noticed that your function returns only x coordinates on the axes twice rather than x and y coordinates at the same time. I invoke the function like this.
"f = figure;
a = axes;
h = plot(t,x);
set(f,'windowbuttonmotionfcn','gpos(a)'); "

Should there be anything wrong with this, please kindly let me know. But as far as I have tried, no errors at all.

To Frank, please note the argument when you invoke
"gpos(h)
set(h,'WindowButtonMotionFcn',@gpos)"

It requires string argument rather function handle. You need axes handle and figure handle as shown below.

f = figure;
a = axes;
plot(something you want)
set(f,'windowbuttonmotionfcn','gpos(a)');

Hope this helps. Please let me know if you have further problems.

[Daniel P.]

I haven't taken a look at the all code yet and I haven't done any testing yet, but there *might* be a bug: see lines 45 and 46. A variable named "left_origin" is defined in line 45, but it is never used.
In line 46, a variable named "left_origin_unitfig" is used. At this point, the variable still has the value it got in line 42. I don't know if that's intended or not.

Regards,
Daniel P.

[Matías Alonso]

This should be native on MATLAB.