as.hexmode(0)[1] "0"as.hexmode(127)[1] "7f"as.hexmode(255)[1] "ff"45 Colors
Colors in R can be defined in many different ways:
- Using names:
colors()gives all available options - Using a hexadecimal RGB code in the form
#RRGGBBAA, e.g.#FF0000FFfor opaque red. Here, the max value is “FF” which corresponds to 255. - Using the
rgb(red, green, blue, alpha)function (outputs a hex number) - Using the
hsv(h, s, v, alpha)function for the HSV color system (also outputs a hex number) - Using integers: these index the output of
palette(), whose defaults can be changed by the user (e.g.palette("cyan", "blue", "magenta", "red"))
45.1 Color names
There is a long list of color names R understands, and can be listed using colors().
They can be passed directly as characters.
Shades of gray are provided as gray0/grey0 (white) to gray100/grey100 (black).
An extra wide PDF with all built-in R colors is available here:
45.2 Hexadecimal codes
Hexadecimal color codes are characters starting with the pound sign, followed by 4 pairs of hex codes representing Red, Green, Blue, and Alpha values. Since RGB values go from 0 to 255, hex goes from 00 to FF. You can convert decimal to hex using as.hexmode():
The last two values for the alpha setting are optional: if not included, defaults to max, i.e. opaque.
45.3 RGB
rgb(0, 0, 1)[1] "#0000FF"Note the default maxColorValue = 1, set to 255 to use the usual RGB range of 0 to 255:
rgb(0, 0, 255, maxColorValue = 255)[1] "#0000FF"45.4 HSV
Color can also be parameterized using the hue, saturation, and value system (HSV). Each range from 0 to 1.
Simplistically: Hue controls the color. Saturation 1 is max color and 0 is white. Value 1 is max color and 0 is black.
hsv(1, 1, 1)[1] "#FF0000"In the following plot, the values around the polar plot represent hue. Moving inwards to the center, saturation changes from 1 to 0. (The plot is produced using the mplot_hsv() function from the rtemis package.)
mplot_hsv()
mplot_hsv(v = 0.5)
45.5 Transparency
An easy way to add transparency to any color is using adjustcolor():
For example, to get 50% transparent blue:
adjustcolor("blue", alpha.f = 0.5)[1] "#0000FF80"“FF” is hex for 255, and “80” in hex is 128, therefore you can also define the above color as “#0000FF80”, i.e. 0 red, 0 green, 255 blue, 128 alpha.