Thread: [Matplotlib-users] plotting numbers on axes in scientific notation

Hi,

How can I plot numbers on the x and y axes in scientific notation?
 I have very large values on the y axis which I'd like to show as 1e9 and
not 1 followed by 9 zeros.

You can use

    def ticklabel_format(self, **kwargs):
        """
        Convenience method for manipulating the ScalarFormatter
        used by default for linear axes.

        Optional keyword arguments:

          =======   =====================================
          Keyword   Description
          =======   =====================================
          *style*   [ 'sci' (or 'scientific') | 'plain' ]
                    plain turns off scientific notation
          *axis*    [ 'x' | 'y' | 'both' ]
          =======   =====================================

        Only the major ticks are affected.
        If the method is called when the
        :class:`~matplotlib.ticker.ScalarFormatter` is not the
        :class:`~matplotlib.ticker.Formatter` being used, an
        :exc:`AttributeError` will be raised with no additional error
        message.

        Additional capabilities and/or friendlier error checking may
        be added.

        """

anirudh vij wrote:
> Hi,
>
> How can I plot numbers on the x and y axes in scientific notation?
>  I have very large values on the y axis which I'd like to show as 1e9 
> and not 1 followed by 9 zeros.
>
>
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-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

Le mardi 09 septembre 2008 à 08:26 -0400, Michael Droettboom a écrit :
> You can use
> 
>     def ticklabel_format(self, **kwargs):
It did not figure how to use that!
I've tried in ipython :
        import numpy as np
        t = np.linspace(0,1,1024)
        f = np.sin(10*t)/1e5
        plot(t,f)
        ax = gca()
        ax.ticklabel_format(style='sci', axis='y')
        show()

but the yticklabels are still in plain notation...
I've googled, but I still can not find where I am wrong!
-- 
Fabrice Silva <si...@lm...>
LMA UPR CNRS 7051

Fabrice Silva wrote:
> Le mardi 09 septembre 2008 à 08:26 -0400, Michael Droettboom a écrit :
>> You can use
>>
>>     def ticklabel_format(self, **kwargs):
> It did not figure how to use that!
> I've tried in ipython :
>         import numpy as np
>         t = np.linspace(0,1,1024)
>         f = np.sin(10*t)/1e5
>         plot(t,f)
>         ax = gca()
>         ax.ticklabel_format(style='sci', axis='y')

           ax.yaxis.major.formatter.set_powerlimits((0,0))

>         show()
> 
> but the yticklabels are still in plain notation...
> I've googled, but I still can not find where I am wrong!

Yes, this is confusing. The problem is that the "scientific" style uses 
scientific notation only for sufficiently large or small numbers, with 
thresholds determined by the powerlimits parameter.  The line I added 
above will force scientific notation.

The ticklabel_format method needs another kwarg to enable setting the 
powerlimits.

Eric

Eric Firing wrote:
> Fabrice Silva wrote:
>> Le mardi 09 septembre 2008 à 08:26 -0400, Michael Droettboom a écrit :
>>> You can use
>>>
>>>     def ticklabel_format(self, **kwargs):
>> It did not figure how to use that!
>> I've tried in ipython :
>>         import numpy as np
>>         t = np.linspace(0,1,1024)
>>         f = np.sin(10*t)/1e5
>>         plot(t,f)
>>         ax = gca()
>>         ax.ticklabel_format(style='sci', axis='y')
> 
>            ax.yaxis.major.formatter.set_powerlimits((0,0))
> 
>>         show()
>>
>> but the yticklabels are still in plain notation...
>> I've googled, but I still can not find where I am wrong!
> 
> Yes, this is confusing. The problem is that the "scientific" style uses 
> scientific notation only for sufficiently large or small numbers, with 
> thresholds determined by the powerlimits parameter.  The line I added 
> above will force scientific notation.
> 
> The ticklabel_format method needs another kwarg to enable setting the 
> powerlimits.

Done in svn 6148.  I called the kwarg 'scilimits' to emphasize that it 
works with the 'sci' style; if there are comments to the effect that I 
should have called it 'powerlimits' for consistency with the 
corresponding ScalarFormatter method, I can change it.

With the change in svn, instead of the line I added above, your call to 
ticklabel_format would be:

ax.ticklabel_format(style='sci', scilimits=(0,0), axis='y')

Eric