ck_apply_grid: Apply a climatekit Index Function Over a SpatRaster

In climatekit: Unified Climate Indices for Temperature, Precipitation, and Drought

Apply a climatekit Index Function Over a SpatRaster

Description

Compute a daily climatekit index function for every cell in a SpatRaster x whose layers represent successive days, and return the per-period results as a SpatRaster. The supplied function fun must accept a numeric vector and a Date vector and return a data frame with period and value columns (the standard climatekit shape).

Usage

ck_apply_grid(x, fun, dates, ...)

Arguments

x	A SpatRaster. Layers correspond one-to-one with dates.
fun	A ⁠ck_*⁠ function (or any function with the same signature: numeric vector + Date vector + optional named arguments, returning a data frame with period and value).
dates	Date vector of length terra::nlyr(x).
...	Additional named arguments forwarded to fun (for example period = "annual", ref_start, ref_end).

Details

All cells must share the same dates. Cells that are entirely NA are returned as NA. Run-time scales linearly with the number of cells; for very large grids consider sub-setting first.

Value

A SpatRaster with one layer per output period (layer names are the period labels).

Examples

  if (requireNamespace("terra", quietly = TRUE)) {
    dates <- seq(as.Date("2024-01-01"), as.Date("2024-12-31"), by = "day")
    n <- length(dates)
    # Tiny 2x2 SpatRaster of synthetic daily Tmax
    r <- terra::rast(nrows = 2, ncols = 2, nlyrs = n,
                     xmin = 0, xmax = 2, ymin = 0, ymax = 2)
    set.seed(1)
    for (i in seq_len(n)) {
      terra::values(r[[i]]) <- rnorm(4, 15, 5)
    }
    txx_r <- ck_apply_grid(r, ck_txx, dates = dates, period = "annual")
    terra::nlyr(txx_r)
  }

climatekit documentation built on May 9, 2026, 5:08 p.m.