stat_wl_strip: Calculate colours from wavelength.

In aphalo/ggspectra: Extensions to 'ggplot2' for Radiation Spectra

Calculate colours from wavelength.

Description

stat_wl_strip computes color definitions according to human vision and by default plots a narrow, guide-like colour gradient strip based on wavelength. x-scale transformations and axis flipping are currently not supported.

Usage

stat_wl_strip(
  mapping = NULL,
  data = NULL,
  geom = "rect",
  position = "identity",
  ...,
  by.group = FALSE,
  w.band = NULL,
  length.out = 150,
  chroma.type = "CMF",
  na.rm = TRUE,
  show.legend = FALSE,
  inherit.aes = TRUE
)

wl_guide(
  mapping = NULL,
  data = NULL,
  position = "identity",
  ...,
  by.group = FALSE,
  chroma.type = "CMF",
  w.band = NULL,
  length.out = 150,
  ymin = -Inf,
  ymax = Inf,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = TRUE
)

Arguments

mapping	The aesthetic mapping, usually constructed with aes or aes_. Only needs to be set at the layer level if you are overriding the plot defaults.
data	A layer specific dataset - only needed if you want to override the plot defaults.
geom	The geometric object to use display the data.
position	The position adjustment to use for overlapping points on this layer.
...	other arguments passed on to layer. This can include aesthetics whose values you want to set, not map. See layer for more details.
by.group	logical flag If TRUE repeated identical layers are added for each group within a plot panel as needed for animation. If FALSE, the default, a single layer is added per panel.
w.band	waveband object or a list of such objects or NULL.
length.out	The number of steps to use to simulate a continuous range of colours when w.band == NULL.
chroma.type	character one of "CMF" (color matching function) or "CC" (color coordinates) or a chroma_spct object.
na.rm	a logical value indicating whether NA values should be stripped before the computation proceeds.
show.legend	logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes.
inherit.aes	If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders.
ymin, ymax	numeric used as aesthetics for plotting the guide.

Details

By default stat_wl_strip() uses a panel function and ignores grouping as needed for annotation of layers supporting free axis scales. Passing by.group = TRUE as argument changes this behaviour adding the same layer repeatedly for each group as needed for constructing animated plots with functions from package 'gganimate'.

Function wl_guide() is a conveneince wrapper on stat_wl_strip() that also adds the required scale_fill_identity().

As colours are returned as RGB colour definitions, depending on the geometry used the use of scale_fill_identity and/or scale_colour_identity will be necessary for the correct colours to be displayed in the plot.

Value

generic_spect object with new x values plus other computed variables described below.

Computed variables

x

(w.low + wl.high) / 2

wl.low

boundary of waveband

wl.high

boundary of waveband

wl.color

color corresponding to wavelength

wb.color

color corresponding to waveband

wb.name

label of w.band

Default aesthetics

Set by the statistic and available to geoms.

x

..x..

label

as.character(..wb.f..)

xmin

..wl.low..

xmax

..wl.high..

fill

..wb.color..

Required aesthetics

Required by the statistic and need to be set with aes().

x

numeric, wavelength in nanometres

Note

As only one colour scale can exist within a "gg" object, using this scale prevents the mapping to the colour aesthetic of factors in data to create a grouping.

See Also

color_of and fast_color_of_wl, which are used in the implementation.

Other stats functions: stat_color(), stat_find_qtys(), stat_find_wls(), stat_label_peaks(), stat_peaks(), stat_spikes(), stat_wb_box(), stat_wb_column(), stat_wb_contribution(), stat_wb_hbar(), stat_wb_irrad(), stat_wb_label(), stat_wb_mean(), stat_wb_relative(), stat_wb_sirrad(), stat_wb_total(), stat_wl_summary()

Examples

# ggplot() methods for spectral objects set a default mapping for x and y.
ggplot(sun.spct) +
  geom_line() +
  stat_wl_strip(ymax = -0.02, ymin = -0.04) +
  scale_fill_identity()

# on some graphic devices the output may show spurious vertical lines
ggplot(sun.spct) +
  wl_guide(alpha = 0.33, color = NA) +
  geom_line()

aphalo/ggspectra documentation built on June 10, 2025, 4:56 p.m.