Two questions regarding axis scaling

_Jeremy_Conlin1 · September 12, 2008, 8:16pm

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

_Jeff_Whitaker1 · September 12, 2008, 8:31pm

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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_Jeremy_Conlin1 · September 13, 2008, 3:58am

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

···

On Fri, Sep 12, 2008 at 4:31 PM, Jeff Whitaker <jswhit@…146…> 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

_Jeff_Whitaker1 · September 13, 2008, 12:49pm

Jeremy Conlin 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

···

On Fri, Sep 12, 2008 at 4:31 PM, Jeff Whitaker <jswhit@...146... > <mailto:jswhit@…146…>> wrote:

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

John_Owens · November 24, 2008, 2:46am

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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_Jae-Joon_Lee1 · November 24, 2008, 6:01am

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