Matplotlib polar axis offset

Question

I was wondering if it is possible to compensate for the beginning of the radial axis or move it outside the graph.

This is what I hope to achieve:

And this is what I have now.

I read the documentation and various topics on SO, but I did not find anything useful. Does this mean that it is not even possible if it is not mentioned anywhere.

Thanks in advance.

EDIT (added code snippet used to create the chart):

ax = fig.add_subplot(111, projection='polar') ax.set_theta_zero_location('N') ax.set_theta_direction(-1) ax.plot(X,lines[li]*yScalingFactor,label=linelabels[li],color=color,linestyle=ls) 

Answer 1

I'm not sure if you can adjust the polar plot . But here is a workaround based on the last example given here: Floating Axes .

I have included explanatory comments in the code, if you copy / paste it, it should work as is:

 import mpl_toolkits.axisartist.floating_axes as floating_axes from matplotlib.projections import PolarAxes from mpl_toolkits.axisartist.grid_finder import FixedLocator, \ MaxNLocator, DictFormatter import numpy as np import matplotlib.pyplot as plt # generate 100 random data points # order the theta coordinates # theta between 0 and 2*pi theta = np.random.rand(100)*2.*np.pi theta = np.sort(theta) # "radius" between 0 and a max value of 40,000 # as roughly in your example # normalize the r coordinates and offset by 1 (will be clear later) MAX_R = 40000. radius = np.random.rand(100)*MAX_R radius = radius/np.max(radius) + 1. # initialize figure: fig = plt.figure() # set up polar axis tr = PolarAxes.PolarTransform() # define angle ticks around the circumference: angle_ticks = [(0, r"$0$"), (.25*np.pi, r"$\frac{1}{4}\pi$"), (.5*np.pi, r"$\frac{1}{2}\pi$"), (.75*np.pi, r"$\frac{3}{4}\pi$"), (1.*np.pi, r"$\pi$"), (1.25*np.pi, r"$\frac{5}{4}\pi$"), (1.5*np.pi, r"$\frac{3}{2}\pi$"), (1.75*np.pi, r"$\frac{7}{4}\pi$")] # set up ticks and spacing around the circle grid_locator1 = FixedLocator([v for v, s in angle_ticks]) tick_formatter1 = DictFormatter(dict(angle_ticks)) # set up grid spacing along the 'radius' radius_ticks = [(1., '0.0'), (1.5, '%i' % (MAX_R/2.)), (2.0, '%i' % (MAX_R))] grid_locator2 = FixedLocator([v for v, s in radius_ticks]) tick_formatter2 = DictFormatter(dict(radius_ticks)) # set up axis: # tr: the polar axis setup # extremes: theta max, theta min, r max, r min # the grid for the theta axis # the grid for the r axis # the tick formatting for the theta axis # the tick formatting for the r axis grid_helper = floating_axes.GridHelperCurveLinear(tr, extremes=(2.*np.pi, 0, 2, 1), grid_locator1=grid_locator1, grid_locator2=grid_locator2, tick_formatter1=tick_formatter1, tick_formatter2=tick_formatter2) ax1 = floating_axes.FloatingSubplot(fig, 111, grid_helper=grid_helper) fig.add_subplot(ax1) # create a parasite axes whose transData in RA, cz aux_ax = ax1.get_aux_axes(tr) aux_ax.patch = ax1.patch # for aux_ax to have a clip path as in ax ax1.patch.zorder=0.9 # but this has a side effect that the patch is # drawn twice, and possibly over some other # artists. So, we decrease the zorder a bit to # prevent this. # plot your data: aux_ax.plot(theta, radius) plt.show() 

This will create the following graph:

You will need to adjust the axis labels to fit your requirements.
I scaled the data, because otherwise the same problem would have arisen as in your plot - the inner, empty circle would be scaled to a point. You can try zooming with a polar graph and simply place custom labels on the radial axis to achieve a similar effect.