Multiple x-axis, which are nonlinear to each other

Question

I am trying to plot a figure with two x-axis, which are non-linear to each other, with matplotlib. The plot I want to get is like this:

Plot

Basically, the age is dependent on red shift. It's non linear and need to be calculated. I want to make both age and red shift as x-axis. How can I make it?

score 4 · Accepted Answer · edited Sep 20 '15 at 17:08

4

The function twiny() may be what you're looking for.

import matplotlib.pyplot as plt
plt.loglog(range(100))
ax1 = plt.gca()
ax2 = ax1.twiny()
ax2.set_xticks([100,80,50])
ax2.set_xticklabels(['0','1','2'])
ax1.set_xlabel('redshift')
ax2.set_xlabel('age')
plt.show()

edited Sep 20 '15 at 17:08

Max Leske

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answered Feb 13 '13 at 03:28

Kyler Brown

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I did, but was unable to post the plot as I lack the reputation. – Kyler Brown Feb 13 '13 at 05:11
I didn't get the point of this function. It seems that the two x-axis are still linear to each other. – Fxyang Feb 13 '13 at 05:12
1

I guess I assumed by non-linear you meant logarithmic. xticks will place arbitrary ticks, xticklabels can label them. Hope that helps. – Kyler Brown Feb 13 '13 at 05:15
By non-linear, I mean the age can be calculated from redshift through an integral, which is more complicated than logarithmic. – Fxyang Feb 13 '13 at 18:58

score 0 · Answer 2 · edited May 23 '17 at 11:51

I did this like this:

from mpl_toolkits.axes_grid.parasite_axes import SubplotHost 
fig = plt.figure(1, figsize=(figwidth,figheight))
ax = SubplotHost(fig, 1,1,1) 
fig.add_subplot(ax)

#plotting as usual

ax2 = ax.twin() # ax2 is responsible for "top" axis and "right" axis
ax2.axis["right"].toggle(ticklabels=False)
ax2.xaxis.set_major_formatter(FuncFormatter(fmt_zToEta)) #set eta coord format

#with a function for the Z to eta transform for plot labels
def fmt_zToEta(x, pos=None):
    #...
    return transformed_label

I also remember starting off with that redshift example ;-)

I think the SubPlotHost thing is necessary, but I'm not 100% sure, since I ripped this out of an existing (sub)plot of mine without checking if it runs nicely without.

Edit: also, see https://stackoverflow.com/a/10517481/599884

Multiple x-axis, which are nonlinear to each other

2 Answers2