Re: [matplotlib-devel] Better defaults all around?

[Nathaniel S. <nj...@po...>]

On Wed, Nov 26, 2014 at 9:30 AM, Todd <tod...@gm...> wrote:
> On Sat, Nov 22, 2014 at 12:22 AM, Nathaniel Smith <nj...@po...> wrote:
>>
>> - Default line colors: The rgbcmyk color cycle for line plots doesn't
>> appear to be based on any real theory about visualization -- it's just
>> the corners of the RGB color cube, which is a highly perceptually
>> non-uniform space. The resulting lines aren't terribly high contrast
>> against the default white background, and the different colors have
>> varying luminance that makes some lines "pop out" more than others.
>>
>> Seaborn's default is to use a nice isoluminant variant on matplotlib's
>> default:
>>
>> http://web.stanford.edu/~mwaskom/software/seaborn/tutorial/aesthetics.html
>> ggplot2 uses isoluminant colors with maximally-separated hues, which
>> also works well. E.g.:
>>
>> http://www.cookbook-r.com/Graphs/Colors_%28ggplot2%29/ggplot2_scale_hue_colors_l45.png
>
> About this, I am not expert so forgive me if this is nonsensical.  However,
> it would seem to me that these requirements are basically the same as the
> requirements for the new default colormap that prompted this whole
> discussion.  So, rather than create two inconsistent set of colors that
> accomplish similar goals, might it be better to instead use the default
> colormap for the line colors?  You could pick "N" equally-spaced colors from
> the colormap and use those as the line colors.

The main differences in requirements are:
- for the color cycle, you want isoluminant colors, to avoid the issue
where one line is glaring bright red and one is barely-visible-grey.
For general-purpose 2d colormaps, though, you almost always want the
luminance to vary to help distinguish colors from each other.
- for the color cycle, there's no problem with using widely separated
hues -- in fact it's usually better b/c it increases contrast between
the different items, and there's no need to communicate an ordering
between them. But if you try to use the whole hue space in a colormap
then you end up with the much-loathed jet.

-n

-- 
Nathaniel J. Smith
Postdoctoral researcher - Informatics - University of Edinburgh
http://vorpus.org