From: André Dankert [mailto:[email protected]]
Sent: Friday, August 19, 2011 04:12
I have a minor style problem, but, nevertheless, I can't solve it with googles
help. I want to have a minimum precision displayed on my ticks, i.e. if the
ticks are -1,-0.5,0,0.5,1 it should be displayed this way instead of
-1.0,-0.5,0.0,0.5,1.0. With the tick formatter I can set the tick precission,
but only for the whole axis (if I set %d for the example, it will be
-1,0,0,0,1). Also I use MaxNLocator, so I don't predefine the ticks (I thought
it's more convinient to use this already done procedure instead of writing my
own), so I'm more flexible, for example when I zoom in, but therefore I don't
even know, which the maximum precision is.
Possible solutions would be:
1. There is a number precision definition (something like %x.xf) which
produces numbers with minimum precision (again -1.0000 becomes -1 and 2.47300
becomes 2.473)
2. Extract by MaxNLocator defined ticks, edit them accordingly and reassign
them (which would be still a lot of work)
I even checked for solutions in Latex (because I use Latex string coding), but
this is even more inflexible, when it comes to numbers. But maybe someone
knows anything.
I took a third approach in the attachment, deriving a new formatter class from
ScalarFormatter. That's more complicated, but it preserves the offset and
other features of ScalarFormatter. It works for me with or without MathText
enabled; I haven't tested it with usetex on. Note that I overrode a private
method, so future breakage may be more likely than it would be otherwise. I
hope it helps.
import numpy as np
import matplotlib.ticker as mticker
class RStripScalarFormatter(mticker.ScalarFormatter):
"""
Formats as ScalarFormatter but without trailing zeros.
The 'format' attribute of ScalarFormatter instances contains the basic
number formatting as well as the formatting for TeX or MathText. Here we
separate those into the 'format' and 'wrapformat' attributes, respectively.
"""
# Code adapted from mticker.ScalarFormatter.
def __init__(self, useOffset=True, useMathText=False):
mticker.ScalarFormatter.__init__( self, useOffset=useOffset,
useMathText=useMathText )
if self._usetex:
self.wrapformat = '$%s$'
elif self._useMathText:
self.wrapformat = '$\mathdefault{%s}$'
else:
self.wrapformat = '%s'
def _set_format(self):
# set the format string to format all the ticklabels
# The floating point black magic (adding 1e-15 and formatting
# to 8 digits) may warrant review and cleanup.
locs = ( (np.asarray(self.locs) - self.offset) /
10**self.orderOfMagnitude ) + 1e-15
maxsigfigs = max( len(str('%1.8f' % loc).split('.')[1].rstrip('0'))
for loc in locs )
self.format = '%1.' + str(maxsigfigs) + 'f'
def pprint_val(self, x):
xp = (x - self.offset) / 10**self.orderOfMagnitude
if np.absolute(xp) < 1e-8:
xp = 0
xpstr = ( (self.format % xp).rstrip('0').rstrip('.')
or '0' ) # If nothing is left, it must've been zero.
return self.wrapformat % xpstr
if __name__ == '__main__':
import matplotlib.pyplot as plt
plt.plot([-0.005, 0.02])
axes = plt.gca()
axes.yaxis.set_major_formatter(RStripScalarFormatter())
plt.show()
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