a5_is_valid_cell() checks each value against the A5 index encoding: its
resolution bits must name a resolution, and its face or quintant must
exist. Use it on ids from outside sources, such as a file or a database,
before passing them to other functions. a5_cell() accepts any 16-digit
hex string, so an a5_cell vector can hold values that are not cells.
Arguments
- x
An a5_cell vector or a character vector of hex strings. For
a5_is_valid(), also an a5_cell_list or an a5_covering.
Value
A logical vector the length of x. NA where x is NA; for
an a5_cell_list, NA where an element holds NA and no invalid cell;
for an a5_covering, NA for a missing covering.
Hex strings that are not 16 hex digits are FALSE.
Details
a5_is_valid() checks any a5R object, returning one value per element:
an a5_cell vector or hex strings: whether each value is a cell, as
a5_is_valid_cell().an a5_cell_list: whether every cell in each element is valid. An empty element is valid.
an a5_covering: whether each covering is well formed: every stored value but a trailing compaction marker is a valid cell, no cell is finer than the covering's resolution, and the cells are sorted in curve order without overlapping. a5R always builds coverings this way; the check is for coverings assembled by hand, as the covering functions rely on it. A covering need not be fully compacted to be valid.
The world cell (id 0, resolution -1) is valid: it has no boundary, but
a5_cell_to_parent() returns it as the parent of the resolution-0 cells.
Validity says nothing about which index version an id was written with:
ids from a5R before 1.0 are valid cells in a different place. See
a5_migrate().
Examples
cell <- a5_lonlat_to_cell(-3.19, 55.95, resolution = 10)
a5_is_valid_cell(cell)
#> [1] TRUE
a5_is_valid_cell(c(a5_u64_to_hex(cell), "fd00000000000000", "not_a_cell", NA))
#> [1] TRUE FALSE FALSE NA
a5_is_valid(a5_cell_to_children(cell, simplify = FALSE))
#> [1] TRUE