Re: [Matplotlib-users] 'bug' in labelling axes for data with small variation?

[Matt N. <new...@ca...>]

> > I agree it's a bug.  It's not immediately clear to me what the labels
> > should be though
> >
> >  1.0000000002
> >  1.0000000004
> >  1.0000000006
> >
> > and so on?  That takes up a lot of room.  Granted, correct but ugly
> > is better than incorrect but pretty, but I'm curious if there is a
> > better way to format these cases.  Perhaps ideal would be an indicator
> > at the bottom or top of the y axis that read '1+' and then use 2e-9,
> > 4e-9, etc as the actual tick labels.  Do you agree this is ideal?

More likely, the plot should be of 1-x, not x, with 1 subtracted
from the data before being sent to the plot.  Would you use
seconds-since-1970 to make a plot versus Time with a range of 1
sec and data every millisecond?  The data plotted should be the
"significant digits" after all.

FWIW, a custom tick formatter I've been using is below.  It's a
slight variation on the default, and won't solve the space
needed to display "1 + n*1.e-9", but it will do a reasonable job
of picking the number of significant digits to show based on the
data range for the Axis.  It could be expanded....

--Matt

! def myformatter(self, x=1.0, axis=None):
!     """ custom tick formatter to use with FuncFormatter():
!     x     value to be formatted
!     axis  Axis instance to use for formatting
!     """
!     fmt = '%1.5g'
!     if axis == None: 
!         return fmt % x
!     
!     # attempt to get axis span (range of values to format)
!     delta = 0.2
!     try:
!         ticks = axis.get_major_locator()()
!         delta = abs(ticks[1] - ticks[0])
!     except:
!         try:
!             delta = 0.1 * axis.get_view_interval().span()
!         except:
!             pass
! 
!     if   delta > 99999:     fmt = '%1.6e'
!     elif delta > 0.99:      fmt = '%1.0f'
!     elif delta > 0.099:     fmt = '%1.1f'
!     elif delta > 0.0099:    fmt = '%1.2f'
!     elif delta > 0.00099:   fmt = '%1.3f'
!     elif delta > 0.000099:  fmt = '%1.4f'
!     elif delta > 0.0000099: fmt = '%1.5f'
!     
!     s =  fmt % x
!     s.strip()
!     s = s.replace('+', '')
!     while s.find('e0')>0: s = s.replace('e0','e')
!     while s.find('-0')>0: s = s.replace('-0','-')
!
!     return s