Maps one of the viridis colour palettes, or a user-specified palette to values. Viridis colour maps are created by Stéfan van der Walt and Nathaniel Smith. They were set as the default palette for the 'Python' 'Matplotlib' library, introduced at SciPy 2015 conference <http://scipy2015.scipy.org/ehome/index.php?eventid=115969&>. Other palettes available in this library have been derived from 'RColorBrewer' <https://CRAN.R-project.org/package=RColorBrewer> and 'colorspace' <https://CRAN.R-project.org/package=colorspace> packages.
