rescale_diverge: Rescale diverge

In anthonynorth/rdeck: Deck.gl Widget

Rescale diverge

Description

Creates a diverging scale with defined centre / midpoint. Similar to rescale_center(), key difference is the output palette / range is piecewise linear (with respect to breaks) and the entire output range is always used.

Usage

rescale_diverge(scale, center = 0)

Arguments

scale	<scale> a scale object
center	<number> the center of the scale input

Centring vs Diverging

The plot below shows how rescale_center() and rescale_diverge() distort the scale output. The input scale in this case is power_scale(limits = -36:4); this scale is centred and diverged at 0.

The plot on the left shows the mapping between the input -36:4 (x axis) and output 0:1 (y axis). The plot on the right is a linear representation of the left and is the space that rdeck works in. The input -36:4 transformed with power_trans() and rescaled to 0:1. This plot has been included because it's (hopefully) easier to understand.

In the unaltered scale, we see that 0 is mapped to 0.75 in the output, which would be the colour at 0.75 on a colour ramp (e.g. scales::colour_ramp(viridis::viridis(256))(0.75)).

When applying rescale_center() we see that gradient of function has become y = 2/3x in the linear scale, which is 2/3 * scales::rescale(trans$transform(x)) for our data. For rescale_diverge() we see a piecewise scale with the break at center; both sides of center have a different gradient (y = 2/3x and y = 2x - 1) and the full range of y is used.

The colour ramp plot shows the effect rescaling has on a colour palette (in this case viridis).

Note

Category and identity scales aren't supported.

See Also

Other scales: rescale_center(), scale_category(), scale_identity(), scale_linear(), scale_log(), scale_power(), scale_quantile(), scale_quantize(), scale_symlog(), scale_threshold()

Examples

# create a diverging linear scale at 0
linear_diverged <- rescale_diverge(
  scale_color_linear(col, limits = -5:10),
  center = 0
)

# create a diverging log scale at 10
log_diverged <- rescale_diverge(
  scale_log(col, limits = 1:1000),
  center = 10
)

anthonynorth/rdeck documentation built on Feb. 2, 2024, 1:12 p.m.