Re: [Matplotlib-users] scalarFormatter

[Darren D. <dd...@co...>]

John Hunter wrote:

>>>>>>"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
>
>  
>

I strongly support stripping all unnecessary zeros from the labels. It 
seems a clear choice to me, but I would be interested to know if others 
are against it.

The third to last line needs changing, prepare for hackishness:
temp = tup[1][0] + tup[1][1:].lstrip('0') # strip zeros if there is a + 
or - sign
temp.replace('+', '')

The regexpr was more elegant, and I don't mind spending an evening 
learning it so I can continue to work with it. On the other hand, string 
methods are more accessible. Elegant or accessible? What would "upper 
management" pick?