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Matplotlib - logarithmic scale, but require non-logarithmic labels

Asked 2011-06-21T19:57:43.990
24

How can I stop the y-axis displaying a logarithmic notation label on the y-axis?

I'm happy with the logarithmic scale, but want to display the absolute values, e.g. [500, 1500, 4500, 11000, 110000] on the Y-axis. I don't want to explicitly label each tick as the labels may change in the future (I've tried out the different formatters but haven't successfully gotten them to work). Sample code below.

Thanks,

-collern2

import matplotlib.pyplot as plt
import numpy as np

a = np.array([500, 1500, 4500, 11000, 110000])
b = np.array([10, 20, 30, 40, 50])

fig = plt.figure()
ax = fig.add_subplot(1,1,1)
ax.set_yscale('log')

plt.plot(b, a)
plt.grid(True)
plt.show()
python matplotlib
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1 Answer

33

If I understand correctly, 

ax.set_yscale('log')

any of

ax.yaxis.set_major_formatter(matplotlib.ticker.ScalarFormatter())
ax.yaxis.set_major_formatter(matplotlib.ticker.FormatStrFormatter('%d'))
ax.yaxis.set_major_formatter(matplotlib.ticker.FuncFormatter(lambda x, pos: str(int(round(x)))))

should work. '%d' will have problems if the tick labels locations wind up being at places like 4.99, but you get the idea.

Note that you may need to do the same with the minor formatter, set_minor_formatter, depending on the limits of the axes.

answered 2011-06-21T20:42:32.787

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