Using Colors in Plots - R Graphics - page 338

Discussion
Mapping continuous values to a color scale requires a continuously changing palette of colors.
Table 12-2 lists the continuous color and fill scales.

Table 12-2. Continuous fill and color scales

Fill scale Color scale Description

scale_colour_gradient() Two-color gradient

scale_fill_gradient()

scale_fill_gradient2() scale_colour_gradient2() Gradient with a middle color and two colors that diverge
from it

scale_fill_gradientn() scale_colour_gradientn() Gradient with n colors, equally spaced

Notice that we used the muted() function in the examples. This is a function from the scales
package that returns an RGB value that is a less-saturated version of the color chosen.

See Also
If you want use a discrete (categorical) scale instead of a continuous one, you can recode your
data into categorical values. See Recoding a Continuous Variable to a Categorical Variable .

Coloring a Shaded Region Based on Value

Problem
You want to set the color of a shaded region based on the yvalue.

Solution
Add a column that categorizes the yvalues, then map that column to fill . In this example, we'll
first categorize the values as positive or negative:

library(gcookbook) # For the data set

cb <- subset(climate, Source == "Berkeley" )

cb$valence[cb$Anomaly10y >= 0 ] <- "pos"
cb$valence[cb$Anomaly10y < 0 ] <- "neg"

cb