Re: [Matplotlib-users] scalarFormatter

[John H. <jdh...@ac...>]

>>>>> "Darren" == Darren Dale <dd...@co...> writes:

    Darren> With MPL 0.62.4, the following script is yielding a few
    Darren> badly formatted y-axis labels:

    Darren> import matplotlib from matplotlib.matlab import *

    Darren> a=array([2,4,6,8,10,12,14,16,18,20])*1e5 plot(a) show()

    Darren> I tried adding a "print s,m" statement after line 272: m =
    Darren> self._zerorgx.match(s), where s is the original text. Here
    Darren> is the output:

    Darren> 2.0e+005 <_sre.SRE_Match object at 0x01249608> 4.0e+005
    Darren> <_sre.SRE_Match object at 0x01249608> 6.0e+005
    Darren> <_sre.SRE_Match object at 0x01249608> 8.0e+005
    Darren> <_sre.SRE_Match object at 0x01249608> 1.0e+006
    Darren> <_sre.SRE_Match object at 0x01249608> 1.2e+006 None
    Darren> 1.4e+006 None 1.6e+006 None 1.8e+006 None 2.0e+006
    Darren> <_sre.SRE_Match object at 0x01249608>

    Darren> _zerorgx = re.compile('^(.*?)\.?0+(e[+-]\d+)?$'), which is
    Darren> greek to me (and I dont have a good reference on
    Darren> regexp's).

There's a reason Jamie Zawinski said

  Some people, when confronted with a problem, think "I know, I'll use
  regular expressions."  Now they have two problems.


Here's a re-implementation using string methods.  See if it passes all
your tests.  More importantly, do you agree that removing the zeros
etc which aren't necessary to visually parse the number is a good
idea?

class ScalarFormatter(Formatter):
    """
    Tick location is a plain old number.  If viewInterval is set, the
    formatter will use %d, %1.#f or %1.ef as appropriate.  If it is
    not set, the formatter will do str conversion
    """

    def __call__(self, x, pos):
        'Return the format for tick val x at position pos'        
        self.verify_intervals()
        d = abs(self.viewInterval.span())

        return self.pprint_val(x,d)

    def pprint_val(self, x, d):
        #if the number is not too big and it's an int, format it as an
        #int
        if abs(x)<1e4 and x==int(x): return '%d' % x
 
        if d < 1e-2: fmt = '%1.3e'
        elif d < 1e-1: fmt = '%1.3f'
        elif d > 1e5: fmt = '%1.1e'
        elif d > 10 : fmt = '%1.1f'
        elif d > 1 : fmt = '%1.2f'
        else: fmt = '%1.3f'
        s =  fmt % x

        tup = s.split('e')
        if len(tup)==2:
            mantissa = tup[0].rstrip('0').rstrip('.')
            exponent = tup[1].replace('+', '').lstrip('0')
            s = '%se%s' %(mantissa, exponent)
        return s

JDH