Converts cell ids written by a5R before 1.0 (the a5 Rust crate 0.10 and earlier, the "v0" index) to the current, permanent index. A5 1.0 threads its space-filling curve through the cells differently, so cells keep their shape and position but get new ids. The conversion is a cheap bit operation; there is no need to re-index data from its coordinates. The exception is resolution 1, whose 60 cells changed from triangles to pentagons: each migrated resolution-1 id is the new cell containing the old cell's centre.
Arguments
- cell
An a5_cell vector of ids in the v0 index.
Value
An a5_cell vector of the same cells in the current index, the
same length as cell. NA where cell is NA.
Details
A v0 id is still a valid cell in the current index, but in a different place, and nothing in the id records which version wrote it. Migrate stored ids exactly once, as soon as they are read: migrating current ids, or migrating twice, gives wrong cells without any error.
Upstream will retire this conversion in a future version.
See also
a5_cell_from_arrow() to read stored ids.
Examples
# A resolution-8 cell id from a5R 0.6.0
v0 <- a5_cell("59c4780000000000")
a5_migrate(v0)
#> <a5_cell[1]>
#> [1] 59c4280000000000