Thread: [Matplotlib-users] Two questions regarding axis scaling

First question:I know I can do pylab.loglog() to get a log-log plot.  I
would like to create a log-linear plot.  How can I do this?

Second question:
I would like to plot two sequences on the same figure with two different
y-scales, one scale shown on the left and one scale shown on the right.  How
can I do this?

Thanks in advance,
Jeremy

Jeremy Conlin wrote:
> First question:
> I know I can do pylab.loglog() to get a log-log plot.  I would like to 
> create a log-linear plot.  How can I do this?

semilogx or semilogy:


 
  semilogy 
<http://matplotlib.sourceforge.net/matplotlib.pyplot.html#-semilogy>(*args, **kwargs)
 
Make a plot with log scaling on the *y* axis.
>
> Second question:
> I would like to plot two sequences on the same figure with two 
> different y-scales, one scale shown on the left and one scale shown on 
> the right.  How can I do this?

twiny:
 

      ax = twiny
    <http://matplotlib.sourceforge.net/matplotlib.axes.html#Axes-twiny>()
     
    create a twin of Axes
    <http://matplotlib.sourceforge.net/matplotlib.axes.html#Axes> for generating a plot with a shared
    y-axis but independent x axis.  The x-axis of self will have
    ticks on bottom and the returned axes will have ticks on the
    top

-Jeff
>
> Thanks in advance,
> Jeremy 
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-- 
Jeffrey S. Whitaker         Phone  : (303)497-6313
Meteorologist               FAX    : (303)497-6449
NOAA/OAR/PSD  R/PSD1        Email  : Jef...@no...
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On Fri, Sep 12, 2008 at 4:31 PM, Jeff Whitaker <js...@fa...> wrote:

> Jeremy Conlin wrote:
>
>> First question:
>> I know I can do pylab.loglog() to get a log-log plot.  I would like to
>> create a log-linear plot.  How can I do this?
>>
>
> semilogx or semilogy:
>
>
>
>  semilogy <
> http://matplotlib.sourceforge.net/matplotlib.pyplot.html#-semilogy>(*args,
> **kwargs)
>
> Make a plot with log scaling on the *y* axis.
>
>>
>> Second question:
>> I would like to plot two sequences on the same figure with two different
>> y-scales, one scale shown on the left and one scale shown on the right.  How
>> can I do this?
>>
>
> twiny:
>
>
>     ax = twiny
>   <http://matplotlib.sourceforge.net/matplotlib.axes.html#Axes-twiny>()
>       create a twin of Axes
>   <http://matplotlib.sourceforge.net/matplotlib.axes.html#Axes> for
> generating a plot with a shared
>   y-axis but independent x axis.  The x-axis of self will have
>   ticks on bottom and the returned axes will have ticks on the
>   top
>
> -Jeff
>
>>
Thanks for that information, that is what I needed.  But now I come up with
a separate problem.  I have the following in my code:

        pylab.plot(n, S, 'b.', label='x')
        pylab.legend()
        ax2 = pylab.twinx()
        pylab.plot(n, mean, 'r',label="mean")
        ax2.yaxis.tick_right()
        pylab.legend()

Both plots are shown with the appropriate axes, but only the second plot is
listed in the legend.  If I only have the first, then only the first plot
will be listed.  Please help.

Jeremy

Jeremy Conlin wrote:
>
>
> On Fri, Sep 12, 2008 at 4:31 PM, Jeff Whitaker <js...@fa... 
> <mailto:js...@fa...>> wrote:
>
>     Jeremy Conlin wrote:
>
>         First question:
>         I know I can do pylab.loglog() to get a log-log plot.  I would
>         like to create a log-linear plot.  How can I do this?
>
>
>     semilogx or semilogy:
>
>
>
>      semilogy
>     <http://matplotlib.sourceforge.net/matplotlib.pyplot.html#-semilogy>(*args,
>     **kwargs)
>
>     Make a plot with log scaling on the *y* axis.
>
>
>         Second question:
>         I would like to plot two sequences on the same figure with two
>         different y-scales, one scale shown on the left and one scale
>         shown on the right.  How can I do this?
>
>
>     twiny:
>
>
>         ax = twiny
>      
>     <http://matplotlib.sourceforge.net/matplotlib.axes.html#Axes-twiny>()
>           create a twin of Axes
>       <http://matplotlib.sourceforge.net/matplotlib.axes.html#Axes>
>     for generating a plot with a shared
>       y-axis but independent x axis.  The x-axis of self will have
>       ticks on bottom and the returned axes will have ticks on the
>       top
>
>     -Jeff
>
>
> Thanks for that information, that is what I needed.  But now I come up 
> with a separate problem.  I have the following in my code:
>
>         pylab.plot(n, S, 'b.', label='x')
>         pylab.legend()
>         ax2 = pylab.twinx()
>         pylab.plot(n, mean, 'r',label="mean")
>         ax2.yaxis.tick_right()
>         pylab.legend()
>
> Both plots are shown with the appropriate axes, but only the second 
> plot is listed in the legend.  If I only have the first, then only the 
> first plot will be listed.  Please help.
>
> Jeremy 
Jeremy:  The problem is that the legends are plotting on top of each 
other.  Try using 'loc=1' for the first one and 'loc=2' for the second one.

-Jeff

-- 
Jeffrey S. Whitaker         Phone : (303)497-6313
NOAA/OAR/CDC  R/PSD1        FAX   : (303)497-6449
325 Broadway                Boulder, CO, USA 80305-3328

Jeff Whitaker wrote:
> 
> Jeremy Conlin wrote:
>>
>>
>> Thanks for that information, that is what I needed.  But now I come up 
>> with a separate problem.  I have the following in my code:
>>
>>         pylab.plot(n, S, 'b.', label='x')
>>         pylab.legend()
>>         ax2 = pylab.twinx()
>>         pylab.plot(n, mean, 'r',label="mean")
>>         ax2.yaxis.tick_right()
>>         pylab.legend()
>>
>> Both plots are shown with the appropriate axes, but only the second 
>> plot is listed in the legend.  If I only have the first, then only the 
>> first plot will be listed.  Please help.
>>
>> Jeremy 
> Jeremy:  The problem is that the legends are plotting on top of each 
> other.  Try using 'loc=1' for the first one and 'loc=2' for the second
> one.
> 

What if I wanted one legend with both entries in it, rather than two
separate legends with a different entry in each? Is that possible? That's
more desirable than two separate legends.

JDO

-- 
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>
> What if I wanted one legend with both entries in it, rather than two
> separate legends with a different entry in each? Is that possible? That's
> more desirable than two separate legends.
>

Check

http://www.nabble.com/displaying-a-legend-from-a-different-subplot-td18447966.html#a18447966

The legend() function lets you explicitly set what items you want to
show, regardless which axes they are from.

-JJ