Plot a color map legend

Plot a visual legend for an ieegio_colormap object.

The continuous method draws a vertical gradient bar with tick marks on the requested axis side (default left); the bar is rendered flush to the opposite edge. Ticks are placed at the minimum, maximum, and zero (when zero falls strictly inside the range).

The discrete method draws vertically stacked labeled color squares. Labels appear to the right of each square. When there are more labels than max_labels, the excess are shown as "... (N omitted)".

Usage

# S3 method for class 'ieegio_colormap_continuous'
plot(x, data_range = NULL, side = 2L, las = 1L, n_colors = 256L, ...)

# S3 method for class 'ieegio_colormap_discrete'
plot(x, max_labels = NA, cex = 1, border = NA, ...)

Arguments

x

an ieegio_colormap_continuous or ieegio_colormap_discrete object

data_range

numeric(2); overrides the color bar range. Falls back to x$data_range, then to c(0, 1) if still missing.

side

integer; axis side for tick marks (see axis). 2 (left, default) places ticks on the left; 4 on the right.

las

integer; label orientation passed to axis. Default 1 (always horizontal).

n_colors

integer; number of color samples used to render the gradient bar. Default 256.

...

currently unused; reserved for future arguments.

max_labels

integer or NA; maximum number of labels to display in the discrete legend. NA (default) auto-sizes from the current plot-region height.

cex

numeric; character expansion for label text. Default 1.

border

color for the box border in the discrete legend; NA (default) draws no border.

Value

Invisibly returns x.

Examples

# Continuous legend --------------------------------------------------
ct <- as_ieegio_colortable(data.frame(
  Key = c(0L, 50L, 100L),
  R = c(0L, 255L, 255L), G = c(0L, 255L, 0L),
  B = c(255L, 0L, 0L),   A = c(255L, 255L, 255L)
))
lut <- as_ieegio_lookup(data.frame(
  Value = c(-3, 0, 3), Scaled = c(0, 0.5, 1)
))
cm_cont <- as_ieegio_colormap(ct, lookup = lut, data_range = c(-3, 3))
grDevices::pdf(NULL)
plot(cm_cont)
grDevices::dev.off()
#> agg_record_20567477318c 
#>                       2 

# Discrete legend ----------------------------------------------------
ct2 <- as_ieegio_colortable(data.frame(
  Key = 1:4,
  R = c(255L, 0L, 0L, 128L), G = c(0L, 200L, 0L, 0L),
  B = c(0L, 0L, 180L, 180L), A = c(255L, 255L, 255L, 255L)
))
lut2 <- as_ieegio_lookup(data.frame(
  Key   = 1:4,
  Label = c("Cortex", "White matter", "CSF", "Hippocampus")
))
cm_disc <- as_ieegio_colormap(ct2, lookup = lut2)
grDevices::pdf(NULL)
plot(cm_disc)
grDevices::dev.off()
#> agg_record_20567477318c 
#>                       2