Within-Pixel Spectral Quartiles — hsa_spectral

An experimental descriptive composition with equal-band type-7 quartiles computed over the measured bands within each spatial pixel.

Usage

hsa_spectral_quartiles(
  cube,
  palette = "magma",
  stretch = c("percentile", "range", "none"),
  probs = c(0.02, 0.98),
  display_limits = c(0, 1),
  value_label = "input value",
  interpolate = TRUE
)

Arguments

cube: An hsi_cube (from hyperspectR) or a 3-D array with dimensions (rows, cols, bands), of integer or double values. Optional wavelengths metadata must be finite, unique and strictly increasing in nm. Without it, coordinates are band indices. An optional logical spatial mask has dimensions (rows, cols) and no missing entries; FALSE excludes a pixel. Arrays may carry these as attributes; an hsi_cube may carry them as list fields. Nonfinite observations are excluded.
palette: Palette name passed to hsa_palette().
stretch: Contrast stretch: "percentile" (default), "range" or "none".
probs: Percentiles for stretch = "percentile". Default c(0.02, 0.98).
display_limits: Two increasing finite endpoints used as the fixed colour domain for stretch = "none". Default c(0, 1).
value_label: A truthful label for the input values. Default "input value". A reflectance label requires known upstream calibration; numeric range alone cannot establish calibration.
interpolate: Logical; interpolate raster pixels. Default TRUE.

Value

One faceted ggplot object, retaining raw panel values and provenance.

Details

The panels are the 25th percentile, median and 75th percentile. Every band must be finite and the pixel unmasked; validity is shared by all panels. One band is allowed and gives three identical values. Bands have equal weight, regardless of wavelength spacing. These summaries omit spectral ordering, depend on sampling density, and are not confidence intervals or uncertainty estimates. A single stretch pools the three rendered raw panel values; all panels share its domain and legend. With a stretch the legend labels display values on 0-1; with stretch = "none" it labels raw input values in the supplied display_limits domain.

Examples

hsa_spectral_quartiles(hsa_demo_cube())