Possible 'septkey' representation?

[ng-stephen]

By 'septkey' I mean the analogue of quadkey, but with digits 0-6 instead of 0-3.
Is it possible to support a string based representation for hex cells that is akin to google s2's quadkey representation '{BaseCellNumber}/{IndexDigit1}{IndexDigit2}{IndexDigit3}...'?
For example, '20/06434' as an alternate representation of '85283473fffffff'. This representation is effectively what gets fed into the constructCell function. This would be very helpful for filtering in database applications. Thank you!

[ajfriend]

That's basically what I was thinking would be possible with functions like constructCell, getResolution, getBaseCellNumber, and getIndexDigit. You should be able to work with those more interpretable representations easily in your application or language of choice.

What support would you be looking for beyond those functions? Some standardized string representation? That's something I'm less sure about (at least at this point in time). If that's it, can you say more about how or when that would be useful, or what you're missing from the functions listed above?

[ng-stephen]

I'd say that having a standardized string representation serves at least two purposes:

1. It's a human readable system that exposes the hierarchical nature of the cells to people who might not otherwise read the binary specification.
2. It allows hierarchical operations via string methods like truncation and concatenation. This is particularly handy when searching a database for all entries that may match a given prefix. One could do something similar using the cell id and bit shift, but one would have to be careful to shift by threes.

The constructCell, getResolution, getBaseCellNumber, and getIndexDigit functions are available in the C API, but do not seem to be exposed by the python or duckdb bindings where I usually work. I'm more than happy to parse the bits of the cell id myself, but am curious if others might find a string 'septkey' useful.

[ajfriend]

At least to your last point, those functions (constructCell and getIndexDigit) are brand new, and will be included in the H3 v4.4 release of the C library, which should happen in the next few days. They'll be available in the bindings, including Python and DuckDB shortly after.

[isaacbrodsky]

With the exception of constructCell that is not released yet, those functions should be available in both Python and DuckDB. On duckdb it should be e.g. h3_get_resolution.

Would it be easier to truncate a string than to use h3_cell_to_parent? With string truncation you'd need a fixed width base cell (or else the truncation is cell dependent) and to figure out the correct number of characters to trim to (4 plus res?)

[ajfriend]

With the exception of constructCell that is not released yet, those functions should be available in both Python and DuckDB. On duckdb it should be e.g. h3_get_resolution.

getIndexDigit is also currently unreleased, coming in 4.4

[ng-stephen]

Would it be easier to truncate a string than to use h3_cell_to_parent? With string truncation you'd need a fixed width base cell (or else the truncation is cell dependent) and to figure out the correct number of characters to trim to (4 plus res?)

You are right. I get mixed up by the terminology 'parent' vs 'ancestor' and overlooked that function. String truncation would be more complicated. I would use a regex, but cellToParent is cleaner.