scales: colour_ramp – R documentation

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colour_ramp

Fast colour interpolation

Description

Returns a function that maps the interval [0,1] to a set of colours. Interpolation is performed in the CIELAB colour space. Similar to colorRamp(space = 'Lab'), but hundreds of times faster, and provides results in "#RRGGBB" (or "#RRGGBBAA") character form instead of RGB colour matrices.

Usage

colour_ramp(colors, na.color = NA, alpha = TRUE)

Arguments

`colors`	Colours to interpolate; must be a valid argument to `grDevices::col2rgb()`. This can be a character vector of `"#RRGGBB"` or `"#RRGGBBAA"`, colour names from `grDevices::colors()`, or a positive integer that indexes into `grDevices::palette()`.
`na.color`	The colour to map to `NA` values (for example, `"#606060"` for dark grey, or `"#00000000"` for transparent) and values outside of [0,1]. Can itself by `NA`, which will simply cause an `NA` to be inserted into the output.
`alpha`	Whether to include alpha transparency channels in interpolation. If `TRUE` then the alpha information is included in the interpolation. The returned colours will be provided in `"#RRGGBBAA"` format when needed, i.e., in cases where the colour is not fully opaque, so that the `"AA"` part is not equal to `"FF"`. Fully opaque colours will be returned in `"#RRGGBB"` format. If `FALSE`, the alpha information is discarded before interpolation and colours are always returned as `"#RRGGBB"`.

Value

A function that takes a numeric vector and returns a character vector of the same length with RGB or RGBA hex colours.

Examples

ramp <- colour_ramp(c("red", "green", "blue"))
show_col(ramp(seq(0, 1, length = 12)))

scales

Scale Functions for Visualization

v1.1.1

MIT + file LICENSE

Authors

Hadley Wickham [aut, cre], Dana Seidel [aut], RStudio [cph]

Initial release