Implements a new version of symlog that is smooth around linthresh

[mdboom]

Implements a new version of symlog that is smooth around linthresh contributed by ssyr. Also includes a cleaner implementation of the symlog ticker. Closes #396.

[mdboom]

@efiring: Can you elaborate on where the mask is being thrown away? Plotting a masked array does appear to work.

[efiring]

On 09/19/2011 04:02 AM, Michael Droettboom wrote:

@efiring: Can you elaborate on where the mask is being thrown away? Plotting a masked array does appear to work.

Every use of np.asarray throws away the mask, starting with the first
line in transform(), 327.

I have not tested in actual use, so maybe this is being compensated or
taken into account somewhere else; but based on looking at the code, it
appears to be an anomaly in the SymmetricalLogTransform family.

[mdboom]

Ok. It doesn't seem to make any practical difference, but I've removed the "asarray" calls in the transformation functions.

[WeatherGod]

Those asarray() calls wouldn't change anything. I think it is the calls to asarray() for the returns that could be the issue. I don't see why we even need a call to asarray() there (except possibly for the second return, but that should still be asanyarray()

[efiring]

Ben, I don't see how you can say those initial asarray calls don't change anything; they are explicitly throwing away any mask at the start.

[WeatherGod]

Sorry, I wasn't clear... they don't do anything useful for the code and are completely unnecessary.

[mdboom]

I've removed all of the redundant "asarray"s. I believe this pull is ready to merge now.