Skip to contents

Lattice alignment of two grids

Source: R/lattice.R
is_aligned.Rd

Two grids share a lattice when their cell boundaries coincide: the resolutions are commensurate (one is an exact integer multiple of the other, in x and in y) and the origins differ by a whole number of the finer cells. When this holds every index operation between the grids is exact integer arithmetic. The test is symmetric.

Usage

is_aligned(
  dimension,
  extent = NULL,
  dimension2,
  extent2 = NULL,
  tol = lattice_tol()
)

Arguments

dimension

integer ncol, nrow

extent

numeric extent xmin,xmax,ymin,ymax

dimension2

dimension of the second grid (ncol, nrow)

extent2

extent of the second grid (xmin, xmax, ymin, ymax), NULL for unit cell space

tol

relative tolerance for whole-number tests

Value

logical

Details

Note that alignment is not containment: a grid may be aligned to another and lie entirely outside it. Use intersect_extent() for overlap.

See also

grid_offset(), snap_grid(), resize_grid(), grid_tiles()

Examples

is_aligned(c(10L, 10L), c(0, 10, 0, 10), c(5L, 5L), c(2, 7, 2, 7))
#> [1] TRUE
is_aligned(c(10L, 10L), c(0, 10, 0, 10), c(5L, 5L), c(2.5, 7.5, 2, 7))
#> [1] FALSE
## coarser grid on the same lattice
is_aligned(c(10L, 10L), c(0, 10, 0, 10), c(2L, 2L), c(0, 10, 0, 10))
#> [1] TRUE