R: Matplotlib 'viridis' color map

viridis {viridisLite} | R Documentation

## Matplotlib 'viridis' color map

### Description

This function creates a vector of `n` equally spaced colors along the Matplolib 'viridis' color map created by Stéfan van der Walt and Nathaniel Smith. This color map is designed in such a way that it will analytically be perfectly perceptually-uniform, both in regular form and also when converted to black-and-white. It is also designed to be perceived by readers with the most common form of color blindness.

### Usage

    viridis(n, alpha = 1, begin = 0, end = 1, direction = 1, option = "D")

    viridisMap(n = 256, alpha = 1, begin = 0, end = 1, direction = 1,
      option = "D")

    magma(n, alpha = 1, begin = 0, end = 1, direction = 1)

    inferno(n, alpha = 1, begin = 0, end = 1, direction = 1)

    plasma(n, alpha = 1, begin = 0, end = 1, direction = 1)

### Arguments

`n` | The number of colors (≥ 1) to be in the palette.
`alpha` | The alpha transparency, a number in [0,1], see argument alpha in `hsv`.
`begin` | The (corrected) hue in [0,1] at which the viridis colormap begins.
`end` | The (corrected) hue in [0,1] at which the viridis colormap ends.
`direction` | Sets the order of colors in the scale. If 1, the default, colors are ordered from darkest to lightest. If -1, the order of colors is reversed.
`option` | A character string indicating the colormap option to use. Four options are available: "magma" (or "A"), "inferno" (or "B"), "plasma" (or "C"), and "viridis" (or "D", the default option).

### Details

Here are the color scales:

`magma()`, `plasma()`, and `inferno()` are convenience functions for the other colormap options, which are useful the scale must be passed as a function name.

Semi-transparent colors (0 < alpha < 1) are supported only on some devices: see `rgb`.

### Value

`viridis` returns a character vector, `cv`, of color hex codes. This can be used either to create a user-defined color palette for subsequent graphics by `palette(cv)`, a `col =` specification in graphics functions or in `par`.

`viridisMap` returns a `n` lines data frame containing the red (`R`), green (`G`), blue (`B`) and alpha (`alpha`) channels of `n` equally spaced colors along the 'viridis' color map. `n = 256` by default, which corresponds to the data from the original 'viridis' color map in Matplotlib.

### Author(s)

Simon Garnier: garnier@njit.edu, @sjmgarnier

### Examples

    library(ggplot2)
    library(hexbin)

    dat <- data.frame(x = rnorm(10000), y = rnorm(10000))

    ggplot(dat, aes(x = x, y = y)) +
      geom_hex() + coord_fixed() +
      scale_fill_gradientn(colours = viridis(256, option = "D"))

    # using code from RColorBrewer to demo the palette
    n = 200
    image(
      1:n, 1, as.matrix(1:n),
      col = viridis(n, option = "D"),
      xlab = "viridis n", ylab = "", xaxt = "n", yaxt = "n", bty = "n"
    )

[Package viridisLite version 0.2.0 Index]