Calculates temporal summaries for each time unit over a moving window of cycles. This function is designed for time series where fundamental time **units** (e.g., months) are grouped into repeating **cycles** (e.g., years).
Usage
calculate_roll(
x,
window_size,
freq = 12,
step = 1,
fun = "mean",
name_template = "{prefix}_w{start_window}-{end_window}_u{idx_unit}",
output_prefix = "output",
output_dir = tempdir(),
user_region = NULL,
method = c("auto", "tiled", "terra"),
tile_degrees = 5,
gdal_opt = c("COMPRESS=DEFLATE", "PREDICTOR=3", "NUM_THREADS=ALL_CPUS"),
overwrite = FALSE
)Arguments
- x
A `terra::SpatRaster` object where each layer represents a time **unit**.
- window_size
Integer. The size of the moving window, measured in the number of **cycles**. For example, if the data cycle is annual (`freq = 12`), a `window_size` of 20 represents a 20-year window.
- freq
Integer. The number of time **units** (layers) that constitute one complete **cycle**. Common examples: 12 for monthly units in a yearly cycle, or 24 for hourly units in a daily cycle.
- step
Integer. The number of **cycles** to slide the window by for each iteration. Default is 1.
- fun
Character. The name of the summary function (e.g., "mean"). Default is "mean".
- name_template
A character string defining the template for output filenames, using `glue` syntax. Default: `"{prefix}_w{start_window}-{end_window}_u{idx_unit}"`. Available placeholders are:
`{prefix}`: The value from `output_prefix`.
`{start_window}`: The starting **cycle** index of the window.
`{end_window}`: The ending **cycle** index of the window.
`{idx_unit}`: The index of the time **unit** within the cycle (e.g., the month number).
- output_prefix
A character string for output filenames. Default is "output".
- output_dir
Directory to save the final GeoTIFF files.
- user_region
(Optional) An `sf` or `terra::SpatVector` for clipping.
- method
Processing method: "auto", "tiled", or "terra".
- tile_degrees
(Tiled method only) Approximate size of processing tiles.
- gdal_opt
(Optional) GDAL creation options for GeoTIFFs.
- overwrite
Logical. If `FALSE` (default), stops if output files exist.