inlmisc (version 0.4.3)

GetTolColors: Paul Tol's Color Schemes

Description

This function creates a vector of n colors from qualitative, diverging, and sequential color schemes by Paul Tol (2018).

Usage

GetTolColors(n, scheme = "smooth rainbow", alpha = NULL, start = 0,
  end = 1, bias = 1, reverse = FALSE, blind = NULL, gray = FALSE)

Arguments

n

'integer'. Number of colors to be in the palette. The maximum number of colors in a generated palette is dependent on the specified color scheme, see ‘Details’ section for maximum values.

scheme

'character'. Color scheme name: specify "bright", "vibrant", "muted", "pale", "dark", "light", or "ground cover" for a qualitative color scheme; "sunset", "BuRd", or "PRGn" for a diverging color scheme; and "YlOrBr", "discrete rainbow", or "smooth rainbow" (the default) for a sequential color scheme. Partial string matching is supported so argument may be abbreviated.

alpha

'numeric'. Alpha transparency, values range from 0 (fully transparent) to 1 (fully opaque). Specify as NULL to exclude the alpha channel value from colors.

start, end

'numeric'. Starting and ending color level in the palette, respectively. Specified as a number in the interval from 0 to 1. Applies only to interpolated color schemes: "sunset", "BuRd", "PRGn", "YlOrBr", and "smooth rainbow".

bias

'numeric'. Interpolation bias where larger values result in more widely spaced colors at the high end. See colorRamp function for details.

reverse

'logical'. Whether to reverse the color order in the palette.

blind

'character'. Type of color blindness to simulate: specify "deutan" for green-blind vision, "protan" for red-blind vision, "tritan" for green-blue-blind vision, or "monochromacy" for total-color blindness. A partial-color blindness simulation requires that the dichromat package is available, see dichromat function for additional information. Partial string matching is supported so argument may be abbreviated.

gray

'logical'. Whether to subset the "bright", "vibrant", and "muted" color schemes to work after conversion to gray scale.

Value

Returns an object of class 'Tol' that inherits behavior from the 'character' class. The object is comprised of a 'character' vector of n colors in the RGB color system. Colors are specified with a string of the form "#RRGGBB" or "#RRGGBBAA" where RR, GG, BB, and AA are the red, green, blue, and alpha hexadecimal values (00 to FF), respectively. Attributes of the returned object include: "names", the informal names assigned to colors in the palette, where NULL indicates no color names are specified; "bad", a 'character' string giving the color meant for bad data, in hexadecimal format, where NA indicates no bad color is specified; and "call", an object of class 'call' giving the unevaluated function call (expression) that can be used to reproduce the color palette. Use the eval function to evaluate the "call" argument. A simple plot method is provided for the 'Tol' class that shows a palette of colors using a sequence of shaded rectangles, see ‘Examples’ section for usage.

Details

The maximum number of colors in a palette is: n = 6 for "pale" and "dark"; n = 8 for "bright" and "vibrant"; n = 10 for "muted", "light", "YlOrBr", "BuRd", and "PRGn"; n = 14 for "ground cover"; and n = 24 for "discrete rainbow". For "sunset", "BuRd", "PRGn", "YlOrBr", and "smooth rainbow", a continuous version of the scheme is available that has no limit placed on the number of colors in a palette. The exception to these limits occurs when the gray argument is true: in that case n = 3 for "bright", n = 4 for "vibrant", and n = 5 for "muted". Color schemes "pale", "dark", and "ground cover" are intended to be accessed in their entirety and subset using vector element names. The very specific "ground cover" scheme is a color-blind safe version of the AVHRR global land cover classification (Hansen and others, 1998).

References

Hansen, M., DeFries, R., Townshend, J.R.G., and Sohlberg, R., 1998, UMD Global Land Cover Classification, 1 Kilometer, 1.0: Department of Geography, University of Maryland, College Park, Maryland, 1981-1994.

Tol, Paul, 2018, Colour Schemes: SRON Technical Note, doc. no. SRON/EPS/TN/09-002, issue 3.0, 17 p., accessed August 29, 2018 at https://personal.sron.nl/~pault/data/colourschemes.pdf.

See Also

col2rgb

Examples

# NOT RUN {
cols <- GetTolColors(n = 10)
print(cols)
plot(cols)

# Qualitative color schemes (scheme)
op <- par(mfrow = c(6, 1), oma = c(0, 0, 0, 0))
plot(GetTolColors(7, scheme = "bright"))
plot(GetTolColors(7, scheme = "vibrant"))
plot(GetTolColors(9, scheme = "muted"))
plot(GetTolColors(6, scheme = "pale"))
plot(GetTolColors(6, scheme = "dark"))
plot(GetTolColors(9, scheme = "light"))
par(op)

op <- par(oma = c(1, 0, 0, 0), cex = 0.7)
plot(GetTolColors(14, scheme = "ground cover"))
par(op)

# Diverging color schemes (scheme)
op <- par(mfrow = c(6, 1), oma = c(0, 0, 0, 0))
plot(GetTolColors( 11, scheme = "sunset"))
plot(GetTolColors(255, scheme = "sunset"))
plot(GetTolColors(  9, scheme = "BuRd"))
plot(GetTolColors(255, scheme = "BuRd"))
plot(GetTolColors(  9, scheme = "PRGn"))
plot(GetTolColors(255, scheme = "PRGn"))
par(op)

# Sequential color schemes (scheme)
op <- par(mfrow = c(5, 1), oma = c(0, 0, 0, 0))
plot(GetTolColors(  9, scheme = "YlOrBr"))
plot(GetTolColors(255, scheme = "YlOrBr"))
plot(GetTolColors( 23, scheme = "discrete rainbow"))
plot(GetTolColors( 34, scheme = "smooth rainbow"))
plot(GetTolColors(255, scheme = "smooth rainbow"))
par(op)

# Alpha transparency (alpha)
op <- par(mfrow = c(5, 1), oma = c(0, 0, 0, 0))
plot(GetTolColors(34, alpha = 1.0))
plot(GetTolColors(34, alpha = 0.8))
plot(GetTolColors(34, alpha = 0.6))
plot(GetTolColors(34, alpha = 0.4))
plot(GetTolColors(34, alpha = 0.2))
par(op)

# Color levels (start, end)
op <- par(mfrow = c(4, 1), oma = c(0, 0, 0, 0))
plot(GetTolColors(255, start = 0.0, end = 1.0))
plot(GetTolColors(255, start = 0.0, end = 0.5))
plot(GetTolColors(255, start = 0.5, end = 1.0))
plot(GetTolColors(255, start = 0.3, end = 0.9))
par(op)

# Interpolation bias (bias)
op <- par(mfrow = c(7, 1), oma = c(0, 0, 0, 0))
plot(GetTolColors(255, bias = 0.4))
plot(GetTolColors(255, bias = 0.6))
plot(GetTolColors(255, bias = 0.8))
plot(GetTolColors(255, bias = 1.0))
plot(GetTolColors(255, bias = 1.2))
plot(GetTolColors(255, bias = 1.4))
plot(GetTolColors(255, bias = 1.6))
par(op)

# Reverse colors (reverse)
op <- par(mfrow = c(2, 1), oma = c(0, 0, 0, 0), cex = 0.7)
plot(GetTolColors(10, reverse = FALSE))
plot(GetTolColors(10, reverse = TRUE))
par(op)

# Color blindness (blind)
op <- par(mfrow = c(5, 1), oma = c(0, 0, 0, 0))
plot(GetTolColors(34, blind = NULL))
plot(GetTolColors(34, blind = "deutan"))
plot(GetTolColors(34, blind = "protan"))
plot(GetTolColors(34, blind = "tritan"))
plot(GetTolColors(34, blind = "monochromacy"))
par(op)

# Gray-scale preparation (gray)
op <- par(mfrow = c(6, 1), oma = c(0, 0, 0, 0))
plot(GetTolColors(3, "bright",  gray = TRUE))
plot(GetTolColors(3, "bright",  gray = TRUE, blind = "m"))
plot(GetTolColors(4, "vibrant", gray = TRUE))
plot(GetTolColors(4, "vibrant", gray = TRUE, blind = "m"))
plot(GetTolColors(5, "muted",   gray = TRUE))
plot(GetTolColors(5, "muted",   gray = TRUE, blind = "m"))
par(op)

# }