[Matplotlib-users] default tick behaviour

[matthew a. <ma...@ca...>]

Hi,

I am happily using matplotlib-0.50e. I tried eps output and it worked very 
nicely. The problem with plot lines not being clipped by a manual axis in 
the PS backend also seems to have been fixed.

...

I have some feedback on the default tick behaviour. matplotlib seems to
pick a number of ticks, and then divides through to get the tick values.
This results in some ugly long tick labels, making it hard to quickly
gauge the range between two points on a graph.

E.g. if the y range of a plot is 1.927 to 1.948, then matplotlib puts
ticks at (1.927, 1.931, 1.935, ..., 1.948)

I think it would be better (and closer to the plotting behaviour of 
other software) if matplotlib picked ticks that were "round", even if that 
means the endpoints of the axes are slightly outside the range of the 
data.

So the ticks for the example above would become:
(1.925, 1.930, 1.935, ..., 1.950)

I guess this would be more complicated to implement than the current 
algorithm, but it would make life easier when interpreting graphs from 
matplotlib!

...

Another slight niggle. If I set the axis range manually, then if a data
point is exactly equal to the end of the axis range then it won't be 
plotted. Making the axis range slightly longer is clumsy. This also 
violates the principle of least surprise, because automatic axis ranges do 
not have this behaviour. A simple way to see the problem is to compare the 
output of the two plots below:

>>> xvals = arange(0.0, 1.0, 0.1)
>>> plot(xvals, [sin(x) for x in xvals])
[<matplotlib.lines.Line2D instance at 0x93fa844>]
>>> show()
>>> plot(xvals, [sin(x) for x in xvals])
[<matplotlib.lines.Line2D instance at 0x9249d2c>]
>>> autoaxis = axis()
>>> autoaxis
[0.0, 0.90000000000000002, 0.0, 0.80000000000000004]
>>> axis(autoaxis)
>>> show()

Presumably the logic for picking the datapoints to plot should use <= not
<.

Cheers,
Matthew.