getColors: Generate a three-color gradient palette

In troyhill/EvergladesEBM: Everglades Ecosystem-Based Management

Generate a three-color gradient palette

Description

Generate a three-color gradient palette

Usage

getColors(
  uniqueValues = c(-2:4)/10,
  binSize = 0.025,
  colorGradient = c("red", "white", "blue"),
  threshold = 0,
  type = "continuous"
)

Arguments

uniqueValues	input values (or vector with max/min)
binSize	size of increment between color gradations
colorGradient	vector with three colors that form the gradient
threshold	value of gradient transition. This value will be the middle color listed in 'colorGradient'
type	type of scale to be produced: 'continuous' (equally-sized intervals) or 'interval' (unequal intervals).

Value

A list with color codes and breaks

Examples

getColors(uniqueValues = range(-10:10), binSize = 5)
getColors(uniqueValues = range(-10:10), binSize = 3)
getColors(uniqueValues = range(0:100), binSize = 5, threshold = 50) # odd behavior
getColors(uniqueValues = range(0:99), binSize = 5, threshold = 50)
getColors(uniqueValues = range(-13:67)/100, binSize = 0.025)

### lop-sided categories with unequal sizes
getColors(uniqueValues = c(-365,-30, 0, 10, 30, 60, 365, 400, 700),
 type = 'interval', binSize = 5, threshold = 0)

f <- system.file("ex/elev.tif", package="terra") 
r <- rast(f)
plot(r)


cols <- getColors(uniqueValues = c(minmax(r)), binSize = 40, 
        threshold = mean(c(minmax(r))))
plot(r, breaks = cols$key, col = cols$colors)   

### example with five colors
cols <- getColors(uniqueValues = c(minmax(r)), binSize = 20, 
   threshold = mean(c(minmax(r))),
   colorGradient = c("red", "yellow", "white", "green", "blue"))
plot(r, col = cols$colors, type = 'continuous', breaks = cols$key)

cols <- getColors(uniqueValues = c(100, 195, 200, 205, 300, 350, 450, 550), 
        binSize = 40, # binSize argument is irrelevant if type = 'interval'
        threshold = 200, type = 'interval')
plot(r, breaks = cols$key, col = cols$colors)   

troyhill/EvergladesEBM documentation built on Nov. 19, 2023, 8:39 a.m.