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Plot selected polygon units over several raster layers

Source: R/viz_polygon_seasons.R
wapor_plot_polygon_seasons.Rd

Draws a grid of small maps with one row per polygon unit (for example a farm) and one column per layer of x (for example one seasonal AETI map per season). Every panel of a row shows the same unit at the same size: the layer cropped to the unit's square extent plus buffer, with all polygon outlines of the unit on top. All panels share one colour scale, computed from all pixels of all layers of x, so colours can be compared between units and between layers.

Usage

wapor_plot_polygon_seasons(
  x,
  polygons,
  id_col,
  ids = NULL,
  row_labels = NULL,
  col_labels = NULL,
  title = NULL,
  legend_title = NULL,
  scale = c("continuous", "percentile_stretch"),
  limits = NULL,
  probs = c(0.02, 0.1, 0.25, 0.5, 0.75, 0.9, 0.98),
  palette = "YlGnBu",
  reverse = TRUE,
  line_width = 0.4,
  line_colour = "black",
  buffer = 40,
  legend_size = 3,
  out_file = NULL,
  width = 14,
  height = NULL,
  dpi = 300
)

Arguments

x

SpatRaster (or raster file path) with one layer per column.

polygons

sf object, SpatVector or vector file path. Reprojected to the CRS of x.

id_col

Name of the column that groups polygons into units.

ids

Units to draw, one row each, in this order. Defaults to all units (sorted).

row_labels

Row titles, one per ids, unique. Defaults to ids.

col_labels

Column titles, one per layer of x. Defaults to the layer names.

title

Plot title.

legend_title

Colour bar title. Defaults to title.

scale

"continuous" gradient spread evenly between limits, or "percentile_stretch" gradient anchored at the probs quantiles.

limits

Range of the continuous scale: NULL (2nd to 98th percentile, values outside are drawn in the end colours), "full" (minimum to maximum) or two numbers. Not used for "percentile_stretch", whose range is the first to last quantile.

probs

Quantiles used as colour anchors when scale = "percentile_stretch" (at least two, distinct values).

palette

A grDevices::hcl.pals() palette name or a vector of colours.

reverse

Reverse the palette direction.

line_width, line_colour

Polygon outline width and colour.

buffer

Margin around each unit, in metres. Converted to degrees (1 degree = 111,320 m) when x has a longitude/latitude CRS.

legend_size

Colour bar length relative to the ggplot2 default. With a single row the colour bar is as tall as the panels.

out_file

Optional PNG path to save the plot.

width, height, dpi

Size (inches) and resolution of the saved plot. height = NULL sizes it from the number of rows and columns.

Value

A ggplot object, invisibly when out_file is supplied.

Details

scale = "percentile_stretch" keeps one continuous gradient but anchors its colours at the probs quantiles of x instead of spreading them evenly between the limits: the colour changes fastest where most pixels are, so differences stand out more. The colour bar ticks are the anchor values.

See also

wapor_plot_polygon_grid() for one panel per unit and one layer.

Examples

if (FALSE) { # \dontrun{
seasons <- terra::rast(c("aeti_2018.tif", "aeti_2019.tif", "aeti_2020.tif"))
names(seasons) <- c("2018/2019", "2019/2020", "2020/2021")
wapor_plot_polygon_seasons(
  seasons, "parcels.gpkg", id_col = "farm", ids = c("F053", "F008", "F058"),
  row_labels = c("F053 above ETc", "F008 changes", "F058 below ETc"),
  title = "Seasonal AETI", legend_title = "Seasonal AETI\n(mm)",
  scale = "percentile_stretch", out_file = "sample_farms.png"
)
} # }