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pythonmatplotlibaxis-labels

How to properly display sufficient tick markers using plt.savefig?

After running the code below, the axis tick markers all overlap with each other. At this time, each marker could still have good resolution when zooming popped up by plt.show(). However, the figure saved by plt.savefig('fig.png') would lost its resolution. Can this also be optimised?

enter image description here

from matplotlib.ticker import FuncFormatter
from matplotlib.pyplot import show
import matplotlib.pyplot as plt
import numpy as np

a=np.random.random((1000,1000))

# create scaled formatters / for Y with Atom prefix
formatterY = FuncFormatter(lambda y, pos: 'Atom {0:g}'.format(y))
formatterX = FuncFormatter(lambda x, pos: '{0:g}'.format(x))

# apply formatters 
fig, ax = plt.subplots()
ax.yaxis.set_major_formatter(formatterY)
ax.xaxis.set_major_formatter(formatterX)

plt.imshow(a, cmap='Reds', interpolation='nearest')

# create labels
plt.xlabel('nanometer')
plt.ylabel('measure')
plt.xticks(list(range(0, 1001,10)))
plt.yticks(list(range(0, 1001,10)))

plt.savefig('fig.png',bbox_inches='tight')
plt.show()
Solution

  • I think you can solve it by setting the size of the figure, e.g.

    fig, ax = plt.subplots()
fig.set_size_inches(15., 15.)

    As pointed out by @PatrickArtner in the comments, you can then also avoid the overlap of x-ticks by 

    plt.xticks(list(range(0, 1001, 10)), rotation=90)

    instead of

    plt.xticks(list(range(0, 1001,10)))

    The rest of the code is completely unchanged; the output then looks reasonable (but is too large to upload here).