Convert a point in evapotranspiration-precipitation space to an appropriate cross-blended hypsometric colour

Used to colour HoldridgeHexagons(), and may also be used to aid the interpretation of PET + precipitation data in any graphical context.

Usage

HoldridgeHypsometricCol(pet, prec, opacity = NA)

Arguments

pet, prec

Numeric vectors giving potential evapotranspiration ratio and annual precipitation (in mm).

opacity

Opacity level to be converted to the final two characters of an RGBA hexadecimal colour definition, e.g. #000000FF. Specify a character string, which will be interpreted as a hexadecimal alpha value and appended to the six RGB hexadecimal digits; a numeric in the range 0 (transparent) to 1 (opaque); or NA, to return only the six RGB digits.

Value

Character vector listing RGB or (if opacity != NA) RGBA values corresponding to each PET-precipitation value pair.

References

Palette derived from the hypsometric colour scheme presented at Shaded Relief.

See also

Other Holdridge plotting functions: AddToTernary(), HoldridgePlot(), holdridge, holdridgeClasses

Author

Martin R. Smith (martin.smith@durham.ac.uk)

Examples

HoldridgePlot(hex.col = HoldridgeHypsometricCol)

VeryTransparent <- function(...) HoldridgeHypsometricCol(..., opacity = 0.3)
HoldridgePlot(hex.col = VeryTransparent)
pet <- holdridge$PET
prec <- holdridge$Precipitation
ptCol <- HoldridgeHypsometricCol(pet, prec)
HoldridgePoints(pet, prec, pch = 21, bg = ptCol)