matplotlib-users Mailing List for matplotlib

You want to call "set_yscale('symlog')" on the axes.

Mike

On 08/19/2011 01:07 PM, Jonny Milliken wrote:
> Hi,
>
> I am having some trouble establishing how to use 
> matplotlib.scale.SymmetricalLogScale() to draw a log scale on the 
> positive and negative axis of a plot. Assuming of course that is the 
> correct way to go about it
>
> The code at the moment I am looking at goes something like this, with 
> arbitrary data generated. I need SubplotHost for parasite axis later on.
>
> <><><>
>
> import matplotlib
> import pylab
> import numpy
> from mpl_toolkits.axes_grid.parasite_axes import SubplotHost
>
> fig = pylab.figure(1)
> main = SubplotHost(fig,111)
> fig.add_subplot(main)
>
> x,y = []
> for i in range(100):
>
>     y.append(numpy.random.rand())
>     y.append(-numpy.random.rand())
>     y.append(numpy.random.rand() * 100)
>     y.append(-numpy.random.rand() * 100)
>
>
> x = range(len(y))
>
> main.plot(x,y)
>
> <><><>
>
> At this point I was expecting to be able to run with 
> SymmetricalLogScale in the same way main.set_yscale('log') transforms 
> after the plot but could not work out how to transform it other than:
>
> <><><>
> main.yaxis = matplotlib.scale.SymmetricalLogScale(main.yaxis)
> <><><>
>
> But that obviously didnt work, since SymmetricalLogScale doesnt have 
> get_scale
>
> If anyone could shed some light on the way to invoke this I'd be much 
> obliged!? I havent been able to find an example of it's usage anywhere
>
> Cheers
>
> Jonny
>
>
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As the subject states, I am trying to use a geotiff (shaded relief)
that I have downloaded from seamless.usgs.gov as the background in a
map. Mostly I am just confused about the seamless image projection and
bounds. The metadata defines the latitude of the top and bottom, and
longitude of the left and right sides. I assume that a mercator
projection is what I should use, but I am not sure. The bounds of the
image are also confusing, but they don't match the values specified in
the metadata or the values that I requested.

Any suggestions?

Albert

import numpy as np
import matplotlib.ticker as mticker

class RStripScalarFormatter(mticker.ScalarFormatter):
    """
    Formats as ScalarFormatter but without trailing zeros.

    The 'format' attribute of ScalarFormatter instances contains the basic
    number formatting as well as the formatting for TeX or MathText.  Here we
    separate those into the 'format' and 'wrapformat' attributes, respectively.
    """
    # Code adapted from mticker.ScalarFormatter.

    def __init__(self, useOffset=True, useMathText=False):
        mticker.ScalarFormatter.__init__( self, useOffset=useOffset,
                                          useMathText=useMathText )
        if self._usetex:
            self.wrapformat = '$%s$'
        elif self._useMathText:
            self.wrapformat = '$\mathdefault{%s}$'
        else:
            self.wrapformat = '%s'

    def _set_format(self):
        # set the format string to format all the ticklabels
        # The floating point black magic (adding 1e-15 and formatting
        # to 8 digits) may warrant review and cleanup.
        locs = ( (np.asarray(self.locs) - self.offset) /
                 10**self.orderOfMagnitude ) + 1e-15
        maxsigfigs = max( len(str('%1.8f' % loc).split('.')[1].rstrip('0'))
                          for loc in locs )
        self.format = '%1.' + str(maxsigfigs) + 'f'

    def pprint_val(self, x):
        xp = (x - self.offset) / 10**self.orderOfMagnitude
        if np.absolute(xp) < 1e-8:
            xp = 0
        xpstr = ( (self.format % xp).rstrip('0').rstrip('.')
                  or '0' )  # If nothing is left, it must've been zero.
        return self.wrapformat % xpstr

if __name__ == '__main__':

    import matplotlib.pyplot as plt

    plt.plot([-0.005, 0.02])
    axes = plt.gca()
    axes.yaxis.set_major_formatter(RStripScalarFormatter())
    plt.show()

On Sun, Aug 21, 2011 at 1:01 PM, Jouni K. Seppänen <jk...@ik...> wrote:
> Jeff Klukas <kl...@wi...> writes:
>
>>   File "/Library/Frameworks/EPD64.framework/Versions/7.1/lib/python2.7/site-packages/matplotlib/dviread.py",
>> line 727, in _register
>>     assert encoding is None
>> AssertionError
>
> This sounds like this issue:
> https://github.com/matplotlib/matplotlib/issues/191
>
> There is a workaround in git commit 708c451 (patch below), which you
> could apply to your local copy of dviread.

It works!  Thanks for a simple fix.

|| Jeff Klukas, Research Assistant
|| Dept. of Physics, Univ. of Wisconsin
|| http://jeff.klukas.net

Hi,

is there a way to define the line width in data units, i.e. no in screen 
based but in data coordinate system based units? This way the line 
thickness would scale during zooming (which is intended!).
This way parallel areas would be much easier to plot.

If this is not possible has anyone found a workaround the get something 
similar?

Thanks
Jakob

Hi, Eric,

Yes, the code you sent works.

Many thanks for your help!

Chad



________________________________
From: Eric Firing <ef...@ha...>
To: mat...@li...
Sent: Sunday, August 21, 2011 2:05 PM
Subject: Re: [Matplotlib-users] tkinter bug?



That's probably why the button was commented out.  I think the problem 
here is that using these gui toolkits is tricky, and the tk examples 
were never worked out adequately.  There are various ways of putting a 
quit button back into the example.  Try the one attached.  If it works 
for you, I will make it replace the present example, and I will delete 
the embedding_in_tk2.py example because it adds nothing of interest.

Eric

On 22/08/2011, at 5:36, Benjamin Root wrote:
> Ok, there has been a lot of useful discussion (for both MacOSX and Windows), but in the end, I want to know this: Is it possible for matplotlib to provide a single, recommended, fully-supported-by-us method for installing our package (possibly for each platform?).  Could it be pip? Or some other option?
> 
> It is kinda sad that the linux install instructions are easier than the other platform instructions, and I don't think we even provide a linux installer.

It's pretty easy using MacPorts (thank you MacPorts maintainers :)

sudo port install py27-matplotlib

Obviously that doesn't help when building a dev version, although you can build out of tree ports.

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