which_equal, which_in
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Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 35/100
- Issue type
- Feature
- Clarity
- Mostly clear
- Activity status
- Stale
- Domain
- data, performance
Research direction
Start with src/utils.c around lines 66-69 and trace the implementations of dt[expr, which=TRUE] and set(dt, which(dt$col==val), "col", new_val). Determine how which_eq could serve these paths without materialising an intermediate logical vector; done means both call patterns return the expected indices and preserve their current behavior.
Written by the indexing model from the issue text.
Description
There is a space for improvement when it comes to dt[expr, which=TRUE] and similar calls like set(dt, which(dt$col==val), "col", new_val).
Function available in https://github.com/Rdatatable/data.table/blob/b9265841edecc6d8d3d0e5428f0bc622a147ba16/src/utils.c#L66-L69 which_eq could be used for that purpose. As a result we can obtain which indices without materialising intermediate logical vector that normally needs to be supplied to which function. Logical vectors are expensive in R as they are basically integers.
It would also be a step towards #852
- Dominant language
- R
- Stars
- 3.9k
- Forks
- 1.1k
- Avg merge
- 14h 4m
- Merged PRs (30d)
- 4
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