matplotlib

Email Archive: matplotlib-users (read-only)

[Matplotlib-users] Add a "Crosshair" to the Canvas? :)

From: Haibao Tang <bao@ug...> - 2004-12-26 04:36

Hi, in some analysis, I really think it useful if you can 
add a crosshair feature so I can visually align the position 
of peaks and falls (like the stock market), and may be not 
hard to include, too. Basically, if the "crosshair" checkbox 
checked, a horizontal and a vertical line will appear with 
the movement of the mouse. 

Bao

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Thread	Author	Date
[Matplotlib-users] Add a "Crosshair" to the Canvas? :)	Haibao Tang <bao@ug...>

Re: [Matplotlib-users] Add a "Crosshair" to the Canvas? :)

From: John Hunter <jdhunter@ac...> - 2004-12-27 19:07

>>>>> "Haibao" == Haibao Tang <bao@...> writes:

    Haibao> Hi, in some analysis, I really think it useful if you can
    Haibao> add a crosshair feature so I can visually align the
    Haibao> position of peaks and falls (like the stock market), and
    Haibao> may be not hard to include, too. Basically, if the
    Haibao> "crosshair" checkbox checked, a horizontal and a vertical
    Haibao> line will appear with the movement of the mouse.

It would be nice to have this feature efficiently across backends.
There is an example which shows you how to do this for an arbitrary
backend

  http://matplotlib.sf.net/examples/cursor_demo.py

but it can be slow because it redraws the entire figure every time you
move the cursor.  This is a general problem with animations in
matplotlib that we are thinking about - see for example
http://sourceforge.net/mailarchive/message.php?msg_id=10330431 .

There is also an example showing how to do this for WX/WXAgg (if
memory serves, you are using wx because it supports chinese
characters).  This uses WX to do the cursoring, which is much more
efficient because you don't have to redraw the figure

  http://matplotlib.sf.net/examples/wxcursor_demo.py

When time permits, it would be nice to add cursoring on each backend
with native drawing of the cursor for efficiency...

JDH