R: Splits a Raster* object into smaller chunks and allows to...

split_replace {geoTS}

R Documentation

Splits a Raster* object into smaller chunks and allows to replace cell values

Description

This function will split a Raster* object into smaller chunks. The size of these chunks (number of cells) is controlled by partPerSide, h or v. Additionally, it allows to replace cell values (valToReplace) within Raster* object by another value of user's choice (replacedBy). When save = TRUE, the resulting cellsToProcess Raster* objects are saved in directory outputPath.

Usage

split_replace(
  raster,
  partPerSide,
  h,
  v,
  outputPath,
  name,
  save = TRUE,
  replace = FALSE,
  valToReplace,
  replacedBy,
  dataType,
  format = "GTiff",
  parallelProcessing = FALSE,
  numCores = 20,
  cellsToProcess,
  ...
)

Arguments

`raster`	Raster* object.
`partPerSide`	integer indicating number of cells in which `raster` will be split in each direction (horizontally and vertically). Use when `nrow(raster)` and `ncol(raster)` are multiples of `partPerSide`.
`h`	integer indicating number of horizontal cells in which `raster` will be split.
`v`	integer indicating number of vertical cells in which `raster` will be split.
`outputPath`	character with full path name where the resulting Raster* objects will be saved.
`name`	character with the name to assign to final products.
`save`	logical, should the output be saved, default is `TRUE`.
`replace`	logical, default `FALSE`, when `TRUE`, `valToReplace` and `replacedBy` must by specified.
`valToReplace`	indicates a value to be replaced across `raster` cells.
`replacedBy`	indicates the value by which `valToReplace` is replaced.
`dataType`	character, output data type. See `dataType`.
`format`	character, output file type, default `"GTiff"`. See `writeFormats`.
`parallelProcessing`	logical, default `FALSE`, when `TRUE` raster splitting is done in parallel. See Details.
`numCores`	numeric indicating the number of cores used in parallel processing.
`cellsToProcess`	numeric vector indicating which smaller cells should be processed/saved. See Details.
`...`	additional arguments used by `writeRaster`.

Details

Before processing any of the cellsToProcess the temporary raster directory is re-directed. Basically, prior to process the i-th cell, at outputPath a new subdirectory is created, which, in turn, is erased automatically once the i-th cell has been processed. As a result of several tests we found that this measure avoids memory overflow.

When partPerSide is used, cellsToProcess = 1:(partPerSide^2). When h and v are used, cellsToProcess = 1:(ncells(raster)/(h*v)). Since the code assumes that nrow(raster) and ncol(raster) are multiples of partPerSide or h and v, respectively, the user must be careful when selecting these parameters.

For parallelProcessing the backend doParallel is employed.

Value