vaster: Tools for Raster Grid Logic

Provides raster grid logic without requiring materialized data. Most raster operations are purely functions of dimension (ncol, nrow) and extent (xmin, xmax, ymin, ymax) - vaster provides these operations as simple functions on numbers, independent of any file format or geospatial library.

Core concepts

A raster grid is defined by two properties:

• dimension: c(ncol, nrow) - the number of columns and rows

• extent: c(xmin, xmax, ymin, ymax) - the bounding box

From these six numbers, all grid geometry can be computed: cell indices, coordinates, resolutions, and spatial queries.

Cell indexing

Cells are numbered from 1, starting at the top-left corner, proceeding right then down (row-major order). This matches the convention used by the raster and terra packages.

Main function families

Cell operations (cells):

• cell_from_xy(), cell_from_row_col(), cell_from_rowcol_combine() - cell index from position

• cell_from_row(), cell_from_col() - all cells in a row or column

• cell_from_extent(), extent_from_cell() - cell/extent conversion

• xy_from_cell(), x_from_cell(), y_from_cell() - coordinates from cell

• rowcol_from_cell(), row_from_cell(), col_from_cell() - row/column from cell

Coordinate operations (coordinates):

• x_from_col(), y_from_row() - coordinate from index

• col_from_x(), row_from_y() - index from coordinate

• x_corner(), y_corner() - corner coordinates of all cells

• x_centre(), y_centre() - centre coordinates of all cells

• xy() - centre coordinates of all cells as a matrix

Grid properties (grid):

• x_res(), y_res() - cell resolution

• n_cell(), n_row(), n_col() - counts

• xlim(), ylim() - extent as 2-element ranges

• x_min(), x_max(), y_min(), y_max() - individual extent edges

• origin() - grid origin (alignment anchor)

Grid modification:

• vcrop() - crop or extend a grid, snapped to alignment

• align_extent() - snap an extent to grid origin

• extent_dimension() - dimension for an aligned extent

• intersect_extent() - overlapping extent of two grids

• snap_extent() / buffer_extent() - snap extent to resolution

Cell adjacency (adjacency):

• adjacency() - neighbour cell indices (queen, rook, or bishop)

GDAL interoperability:

• geo_transform0(), geo_world0() - create geotransform / world file vectors

• world_to_geotransform(), geotransform_to_world() - convert between formats

• extent_dim_to_gt(), gt_dim_to_extent() - convert extent/dimension to/from geotransform

• rasterio0(), rasterio_idx(), raster_sfio() - GDAL RasterIO parameters

• rasterio_to_sfio(), sfio_to_rasterio() - convert between RasterIO formats

• ts_te(), gdal_ts(), gdal_te() - format dimension/extent for GDAL command line

Output and display:

• vaster_long() - cell coordinates as long-form matrix

• vaster_listxyz() - grid as x, y, z list for graphics::image()

• vaster_boundary(), vaster_boundary_cell() - boundary coordinates

• plot_extent(), draw_extent() - plot and interactively draw extents

• extent_vrt() - tile extents from VRT files

Utilities:

• from_xyz() - derive grid dimension and extent from XYZ points

• fit_dims() - compute dimension from aspect ratio and target size

Extent convention

vaster uses extent as c(xmin, xmax, ymin, ymax), which differs from the bbox convention c(xmin, ymin, xmax, ymax). Both represent the same information in different order.

If extent is not provided, the default is c(0, ncol, 0, nrow) - matching the convention adopted by stars, terra, and an improvement on base R's image() which scales to 0-1.

See also

Useful links:

• https://github.com/hypertidy/vaster

• https://hypertidy.github.io/vaster/

• Report bugs at https://github.com/hypertidy/vaster/issues

Author

Maintainer: Michael Sumner mdsumner@gmail.com (ORCID)

Other contributors:

• Robert Hijmans (Wrote original versions of abstract cell operations in raster package) [contributor]