The example here What is the difference between 'log' and 'symlog'? nicely shows how a linear scale at the origin can be used with a log scale elsewhere. I
I assume you want linear near the origin, log farther -- since `symlog' does it the other way around -- I couldn't come up with data that looked good like this, but you can put it together with the axes_grid:
# linear and log axes for the same plot?
# starting with the histogram example from
# http://matplotlib.org/mpl_toolkits/axes_grid/users/overview.html
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable
import numpy as np
# Numbers from -50 to 50, with 0.1 as step
xdomain = np.arange(-50,50, 0.1)
axMain = plt.subplot(111)
axMain.plot(xdomain, np.sin(xdomain))
axMain.set_yscale('log')
axMain.set_ylim((0.01, 0.5))
divider = make_axes_locatable(axMain)
axLin = divider.append_axes("top", size=2.0, pad=0.02, sharex=axMain)
axLin.plot(xdomain, np.sin(xdomain))
axLin.set_xscale('linear')
axLin.set_ylim((0.5, 1.5))
plt.title('Linear above, log below')
plt.show()
