argSort style.multiKeyArgSort
fn
size_t[] multiKeyArgSort(DataFrame frame, string[] by, bool[] descending,
bool nullsLast = false)Sorts the rows of a frame by its key columns: one stable pass per key, last key first, so earlier keys become the tie-break of later ones. Every pass applies the null placement. The frame adapter resolves names and flags; the stable passes themselves are the column-input operation in ddn.df.sort.
Parameters
frame | the frame to sort |
by | the key column names, major first |
descending | per-key direction flags (by.length entries) |
nullsLast | nulls after valid entries in every key |
Returns
the permutation that sorts the rows,
Throws
DataFrameException when a key column is absent or the flag
array length differs from by.