matplotlib-users Mailing List for matplotlib

On Fri, 2004-12-24 at 09:21 -0500, Paul Barrett wrote:
> I therefore propose that we start developing a Python version of DS9. 
> The benefits of a Python version based on matplotlib are TrueType fonts 
> (with arbitrary text rotation), alpha blending, and direct support for 
> numarray.

Sounds like an interesting project.  The first item I'd have on a list
of desired features is, surprise, the ability to load multiple aligned
images and blink between them.

>>>>> "Haibao" == Haibao Tang <ba...@ug...> 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

>>>>> "Istvan" == Istvan Szapudi <sz...@If...> writes:

    Istvan> Hi All, I am fairly new to matplotlib, and I am impressed
    Istvan> with its capabilities.

    Istvan> I have trouble plotting loglog plots with errorbars. I
    Istvan> have the following, program, a slightly modified version
    Istvan> of one given earlier by JDH on 9-28-2004 in this mailing
    Istvan> list:

This is definitely a gotcha that matplotlib needs to be smarted about
handling.  The log zero error is occurring when the transformation is
made on the axes limits and not on the data.  The autoscaler picks the
best min/max for the data coordinates, and will round down or up to
facilitate nice integer ticking.  When you plot with linear coords,
the autoscaler makes it's pick according to linear scaling, and then
when you change scales the old scaling is in effect and the log
transform fails when converting the viewport.

Solution: rescale the axes after changing coords, 
either manually

  ax.set_yscale("log")
  ax.set_xscale("log")
  axis([0.5*min(x), 2*max(x), 0.5*min(y-err), 2*max(y+err)])

or use the autoscaler

  ax.set_yscale("log")
  ax.set_xscale("log")
  ax.autoscale_view()

or set your log coords *before* calling plot

  ax = gca()
  ax.set_yscale("log")
  ax.set_xscale("log")
  errorbar(x,y,err,fmt='o')
  show()

and then the errorbar command will pick a "locator" to handle ticking
and viewport scaling appropriately from the outset.  This is the
approach taken in http://matplotlib.sf.net/examples/log_bar.py .

Until I get this fixed to work automagically, I'll make it a FAQ.

JDH

>>>>> "Edward" == Edward Abraham <Edw...@da...> writes:

    Edward> Interactive use is great, but I need to draw Matlplotlib
    Edward> plots to a window from within a wx application. The
    Edward> example linked to from the screenshots page
    Edward> (embedding_in_wx.py) is broken. I have attached a simple
    Edward> modified version (no toolbar, just a plot). Matplotlib
    Edward> window redraws are quite slow, and the default behaviour
    Edward> is ugly during resizing. The example shows how to modify
    Edward> the FigureCanvas class to redraw only during idle
    Edward> time. This means that there is only one redraw during
    Edward> resizing. The wxagg backend is chosen, as for the simple
    Edward> plot shown here it is quicker than the current
    Edward> implementation of the wx backend.

OK, thanks for letting me know.  I updated the website - the link
should have, and now does, point to examples/embedding_wx2.py.  Note
the matplotlib examples dir, with the src distribution and at
http://matplotlib.sf.net/examples, does contain a few examples showing
how to embed matplotlib into WX/WXAgg.  Eg, examples/embedding_wx2.py
shows how embed use the toolbar as well.

Would you mind if I add your example to the examples subdir?

Thanks!
JDH