release strategy and the color revolution

Development matplotlib-devel
1

Out of curiosity, what are the advantages of the HCL colormap over YlGnBu for continuous values? I’m biased towards YlGnBu because green is my favorite color and want to know what makes HCL objectively better for perceiving values.

I added YlGnBu_r versions of those plots just below yours: http://nbviewer.ipython.org/gist/olgabot/6a619ef21c178801ff77

It seems it’s a little more “extreme” than HCL, as in it lights are lighter and its darks are darker. From the color research, is this less desirable?

···

On Mon, Feb 16, 2015 at 3:38 PM, Eric Firing <efiring@…229…> wrote:

Nathaniel’s January 9 message in that thread (can’t figure out how to

link to it in the archives) had a suggestion that I thought was very

promising, to do something similar to Parula but rotate around the hue

circle the other direction so that the hues would go blue - purple - red

  • yellow. I don’t think we’ve seen an example of exactly what it would

look like, but I reckon it would be similar to the middle colormap here

http://earthobservatory.nasa.gov/blogs/elegantfigures/files/2013/08/three_perceptual_palettes_618.png

(from the elegant figures block series linked above), which I’ve always

found quite attractive.
On 2015/02/16 1:29 PM, Michael Waskom wrote:

Certainly it can be considered–but we have to have a real implementation.

2

Hey Olga,

···

On Tue, Feb 17, 2015 at 6:24 PM, Olga Botvinnik <obotvinn@…55…170…> wrote:

Out of curiosity, what are the advantages of the HCL colormap over YlGnBu for continuous values? I’m biased towards YlGnBu because green is my favorite color and want to know what makes HCL objectively better for perceiving values.

Perceptually, the luminance ramp is probably a bit more linear, but that’s not a huge deal. The main functional advantage to using some kind of Hcl based map is that it lets matplotlib tweak more parameters. This particular Hcl map has a bit more hue variation than YlBuGn, and I think the saturation channel is doing something different than what the colorbrewer maps do. So it appears a little bit more “colorful”, which I think was one of the objectives.

I think there’s some argument for matplotlib creating a novel colormap for its default rather than just using one of the preset colorbrewer ones. It would be nice to have a bit more well-defined visual identity, and having people say “oh hey that’s the matplotlib colormap, it looks really nice!” might have good marketing benefits. I like the colorbrewer palettes and use them often, but it seems kind of boring to take an existing colormap that lots of packages have and make it the default.

I added YlGnBu_r versions of those plots just below yours: http://nbviewer.ipython.org/gist/olgabot/6a619ef21c178801ff77

It seems it’s a little more “extreme” than HCL, as in it lights are lighter and its darks are darker. From the color research, is this less desirable?

Well, that could be changed in the Hcl version by setting different endpoints for the lightness ramp. I was trying to get something similar to parula, which doesn’t cover as extreme of a lightness range and is more saturated on both ends than the color brewer palettes. I would imagine the reasoning for this is that it might let the map represent categorical or divergent data a little bit better without much cost to sequential data, but I am not sure.

Also, if you map a line or scatter plot with YlGnBu, the lightest colors might not be visible on a white background, whereas I think the yellow I used would be ok. This might be something to keep in mind as the map that gets chosen will likely be the default for plt.scatter.

But like I said, I didn’t spend much time thinking about exactly where the endpoints should be, so it’s possible one would want more dynamic luminance range.

Michael

On Mon Feb 16 2015 at 9:28:56 PM Benjamin Root <ben.root@…553…> wrote:

Do remember that I have a PR to add linestyle cycling, which would greatly mitigate problems for colorblindness and non-color publications.

I also prefer it for slideshows as projectors at conferences tend to have crappy colors anyway (was at a radar conference when the projector’s red crapped out while the presenter was building up suspense about the really, really impressive radar image of a supercell on the next slide)

Ben Root

On Feb 16, 2015 7:24 PM, “Michael Waskom” <mwaskom@…865…> wrote:

See here for a quick and dirty implementation that should get a general idea. This probably ins’t the best way to do it – anyone should feel free to build on this.

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On Mon, Feb 16, 2015 at 3:38 PM, Eric Firing <efiring@…229…> wrote:

Nathaniel’s January 9 message in that thread (can’t figure out how to

link to it in the archives) had a suggestion that I thought was very

promising, to do something similar to Parula but rotate around the hue

circle the other direction so that the hues would go blue - purple - red

  • yellow. I don’t think we’ve seen an example of exactly what it would

look like, but I reckon it would be similar to the middle colormap here

http://earthobservatory.nasa.gov/blogs/elegantfigures/files/2013/08/three_perceptual_palettes_618.png

(from the elegant figures block series linked above), which I’ve always

found quite attractive.
On 2015/02/16 1:29 PM, Michael Waskom wrote:

Certainly it can be considered–but we have to have a real implementation.