R: Label peaks and valleys.

stat_label_peaks {ggspectra}

R Documentation

Label peaks and valleys.

Description

stat_labels_peaks finds at which x positions local maxima are located, and adds labels and colors to the data wihtout subsetting. To find local minima, you can use stat_labels_valleys instead.

Usage

stat_label_peaks(
  mapping = NULL,
  data = NULL,
  geom = "text",
  position = "identity",
  ...,
  span = 5,
  ignore_threshold = 0,
  strict = TRUE,
  chroma.type = "CMF",
  label.fmt = "%.3g",
  x.label.fmt = label.fmt,
  y.label.fmt = label.fmt,
  label.fill = "",
  na.rm = TRUE,
  show.legend = FALSE,
  inherit.aes = TRUE
)

stat_label_valleys(
  mapping = NULL,
  data = NULL,
  geom = "text",
  position = "identity",
  ...,
  span = 5,
  ignore_threshold = 0,
  strict = TRUE,
  chroma.type = "CMF",
  label.fmt = "%.3g",
  x.label.fmt = label.fmt,
  y.label.fmt = label.fmt,
  label.fill = "",
  na.rm = TRUE,
  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.
`span`	a peak is defined as an element in a sequence which is greater than all other elements within a window of width span centered at that element. The default value is 5, meaning that a peak is bigger than two consequtive neighbors on each side. Default: 5.
`ignore_threshold`	numeric value between 0.0 and 1.0 indicating the size threshold below which peaks will be ignored.
`strict`	logical flag: if TRUE, an element must be strictly greater than all other values in its window to be considered a peak. Default: FALSE.
`chroma.type`	character one of "CMF" (color matching function) or "CC" (color coordinates) or a `chroma_spct` object.
`label.fmt`	character string giving a format definition for converting values into character strings by means of function `sprintf`.
`x.label.fmt`	character string giving a format definition for converting $x$-values into character strings by means of function `sprintf`.
`y.label.fmt`	character string giving a format definition for converting $y$-values into character strings by means of function `sprintf`.
`label.fill`	character string ot use for labels not at peaks or valleys being highlighted.
`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`.

Details

These stats use geom_text by default as it is the geom most likely to work well in almost any situation without need of tweaking. These statistics work best with geom_text_repel and geom_label_repel from package 'ggrepel' as they are designed so that peak or valley labels will not overlapT any observation in the whole data set. Default aesthetics set by these stats allow their direct use with geom_text, geom_label, geom_line, geom_rug, geom_hline and geom_vline. The formatting of the labels returned can be controlled by the user.

Value

The original data with additional computed variables added.

Computed variables

x.label: x-value at a peak (or valley) formatted as character or otherwise the value passed to label.fill which defaults to an empty string ("").
y.label: y-value at the peak (or valley) formatted as character or otherwise the value passed to label.fill which defaults to an empty string ("").
wl.color: At peaks and valleys, color definition calculated by assuming that x-values are wavelengths expressed in nanometres, otherwise, rgb(1, 1, 1, 0) (transparent white).

Default aesthetics

Set by the statistic and available to geoms.

label: ..x.label..
xintercept: ..x..
yintercept: ..y..
color: black_or_white(..wl.color..)
fill: ..wl.color..

Required aesthetics

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

x: numeric, wavelength in nanometres
y: numeric, a spectral quantity

Note

These stats work nicely together with geoms geom_text_repel and geom_label_repel from package ggrepel to solve the problem of overlapping labels by displacing them. To discard overlapping labels use check_overlap = TRUE as argument to geom_text. By default the labels are character values suitable to be plotted as is, but with a suitable label.fmt labels suitable for parsing by the geoms (e.g. into expressions containing greek letters or super or subscripts) can be also easily obtained.

Examples


# ggplot() methods for spectral objects set a default mapping for x and y.
ggplot(sun.spct) + geom_line() +
  stat_label_peaks(hjust = "left", span = 31, angle = 90, color = "red")
ggplot(sun.spct) + geom_line() +
  stat_label_valleys(hjust = "right", span = 21, angle = 90, color = "blue")

ggplot(sun.spct) + geom_line() +
  stat_peaks(span = 41, shape = 21, size = 3) +
  stat_label_peaks(span = 41, geom = "label", label.fmt = "%3.0f nm") +
  scale_fill_identity() +
  scale_color_identity() +
  expand_limits(y = c(NA, 1))

# using 'ggrepel' to avoid overlaps
# too slow for CRAN checks
## Not run: 
library(ggrepel)

ggplot(sun.spct) + geom_line() +
  stat_peaks(span = 41, shape = 21, size = 3) +
  stat_label_peaks(span = 41, geom = "label_repel", segment.colour = "red",
                   nudge_y = 0.12, label.fmt = "%3.0f nm", vjust = 1) +
  scale_fill_identity() +
  scale_color_identity() +
  expand_limits(y = c(NA, 1))

## End(Not run)

[Package ggspectra version 0.3.12 Index]