filter-by

[genmeblog]

There is an use case where we want to filter based on some column calculations. This calculations can't be done by simple map. For example: we need to filter by (moving) average, or R rank. To flow looks like that:

1. Take a column(s)
2. Produce new temporary column (calculate moving average for example)
3. Filter by this new column, or gather indices and select rows
4. Drop column

Here is concrete case with rank: https://github.com/genmeblog/techtest/blob/master/src/techtest/datatable_dplyr.clj#L554

I can think about solution of filter (filter-by maybe?) which takes a sequence and selects only rows corresponding to the result of predicate.

[cnuernber]

Something like: (filter-by data dataset) where the truthy indexes parts of data an index to keep. Then you could construct data via more efficient means than iterating through the dataset as a sequence of maps.

That alone (have data calculated efficiently) would close the gap a bit further between R and Clojure in the filter example previously on zulip.

[cnuernber]

Is this addressed by your new API?

[genmeblog]

Yes!

[cnuernber]

Addressed by: https://github.com/scicloj/tablecloth