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Re:A friendly guide to colours in data visualisation by splittingTimes on Thursday August 02, 2018 @05:40AM (#17670273)
IBM did research back in the 90s on perceptually-based colormaps and how to best represent various types of data within the color dimensions of luminescence, saturation and hue [1]. For exmpale, they found that,

(1) Hue was not a good dimension for encoding magnitude information, i.e. rainbow color maps are bad.

(2) The mechanisms in human vision responsible for high spatial frequency information processing are luminance channels. If the data to be represented have high spatial frequency, use a colormap which has a strong luminance variation across the data range.

(3) For interval and ratio data, both luminance- and saturation-varying colormaps should produce the effect of having equal steps in data value correspond to equal perceptual steps, but the first will be most effective for high spatial frequency data variations and the second will be most effective for low spatial frequency variations.

===

[1] https://www.research.ibm.com/people/l/lloydt/color/color.HTM

or as pdf:

https://github.com/frankMilde/interesting-reads/blob/master/...

Re:A friendly guide to colours in data visualisation by nerdponx on Thursday August 02, 2018 @07:30AM (#17670664)
As a result, we have the colormap Viridis [0] [1], which is universally one of the best options available. Odd to see a data viz article about color choice in 2018 that doesn't mention Viridis.

[0]: https://www.youtube.com/watch?v=xAoljeRJ3lU

[1]: https://www.youtube.com/watch?v=TojFwkglCKs

Re:A friendly guide to colours in data visualisation by vanderZwan on Thursday August 02, 2018 @01:05PM (#17673168)
And yesterday a paper explaining the process of creating Cividis, an even more CVD friendly iteration, was published on plos.org[0]. It's already in Matplotlib, and available for R[1].

(I submitted it yesterday but it didn't get much traction[2], which makes sense given how specific it is)

[0] http://journals.plos.org/plosone/article?id=10.1371%2Fjourna...

[1] https://github.com/marcosci/cividis

[2] https://news.ycombinator.com/item?id=17667572

Re:A friendly guide to colours in data visualisation by nemetroid on Friday August 03, 2018 @05:50AM (#17678502)
I looked at the paper, and wouldn't really call cividis an iteration of viridis. It's more of a conversion of viridis to "CVD colorspace" (can you say that?), with a few tweaks applied.
Re:A friendly guide to colours in data visualisation by vanderZwan on Friday August 03, 2018 @01:27PM (#17681717)
Well, from my CVD point of view it looks like one ;). It's largely the same except with better color contrast and ability to distinguish detail. But I understand it actually is missing a significant chunk of green hues for the non-colorblind.
Re:A friendly guide to colours in data visualisation by aflam on Thursday August 02, 2018 @09:20AM (#17671169)
Odd indeed, especially since it has all the other useful tools one could use to create palettes. Maybe the target audience is creative people, not us just reusing ad nauseum the same effective palette.
Re:A friendly guide to colours in data visualisation by yiyus on Thursday August 02, 2018 @07:45AM (#17670728)
> rainbow color maps are bad

This is true. But, unfortunately, it is the current standard for many applications.

For example: although a luminance-varying colormap is theoretically better, if my doctor has been analyzing MRI scans using the jet palette for 30 years, I want him to use that color palette when he analyzes mine, instead of using a new one.

I have similar problems in my work, when representing crystallographic textures. The standard way of representing them has multiple problems (not only color choices, but also the use of Euler angles to represent orientations is a huge headache). However, if I publish a paper using a different (objectively better) method, nobody will understand my figures. I have tried including both, but I think almost everybody just ignores the new ones.

Re:A friendly guide to colours in data visualisation by bastijn on Thursday August 02, 2018 @03:33PM (#17674744)
We have been fighting that fight for a while in viz. Spreading the word already in 2012 in "Rainbow colormaps - What are they good for? Absolutely nothing!" [0]

That article/post reached some audience and was referenced quite well at the time. Keep spreading the word I guess.

[0] http://medvis.org/2012/08/21/rainbow-colormaps-what-are-they...

Re:A friendly guide to colours in data visualisation by weinzierl on Thursday August 02, 2018 @10:45AM (#17671824)
I agree with all of this. I encountered one problem when using luminance (either alone or in combination with color) to encode categorical data though:

Luminance inevitably conveys a certain ordering.

A dark black line will be automatically identified as more as important than a light grey line.

This can be desired (and abused), but often I want to present my categories as neutral as possible. I experimented with balancing lightness with other features (like line width) but not with much success.

Re:A friendly guide to colours in data visualisation by jordache on Thursday August 02, 2018 @10:24AM (#17671595)
Neither links work.
Re:A friendly guide to colours in data visualisation by splittingTimes on Thursday August 02, 2018 @11:14AM (#17672064)
Indeed the original IBM link was taken down:

https://web.archive.org/web/20180225102505/https://www.resea...

GitHub displays the PDF just fine on desktop but fails on mobile.