Sorting

arkouda.argsort(pda, algorithm=SortingAlgorithm.RadixSortLSD, axis=0)[source]

Return the permutation that sorts the array.

Parameters:

  • pda (pdarray, Strings, or Categorical) – The array to sort (int64, uint64, or float64)

  • algorithm (SortingAlgorithm, default=SortingAlgorithm.RadixSortLSD) – The algorithm to be used for sorting the array.

  • axis (int_scalars, default=0) – The axis to sort over.

Returns:

The indices such that pda[indices] is sorted

Return type:

pdarray

Raises:

TypeError – Raised if the parameter is other than a pdarray, Strings or Categorical

See also

coargsort

Notes

Uses a least-significant-digit radix sort, which is stable and resilient to non-uniformity in data but communication intensive.

Examples

>>> import arkouda as ak
>>> a = ak.randint(0, 10, 10, seed=1)
>>> a
array([7 9 5 1 4 1 8 5 5 0])

>>> perm = ak.argsort(a)
>>> a[perm]
array([0 1 1 4 5 5 5 7 8 9])

>>> ak.argsort(a, ak.sorting.SortingAlgorithm["RadixSortLSD"])
array([9 3 5 4 2 7 8 0 6 1])

>>> ak.argsort(a, ak.sorting.SortingAlgorithm["TwoArrayRadixSort"])
array([9 3 5 4 2 7 8 0 6 1])
arkouda.coargsort(arrays, algorithm=SortingAlgorithm.RadixSortLSD, ascending=True)[source]

Return the permutation that groups the rows (left-to-right), if the input arrays are treated as columns. The permutation sorts numeric columns, but not Strings or Categoricals — those are grouped, not ordered.

Parameters:

  • arrays (Sequence of Strings, pdarray, or Categorical) – The columns (int64, uint64, float64, Strings, or Categorical) to sort by row.

  • algorithm (SortingAlgorithm, default=SortingAlgorithm.RadixSortLSD) – The algorithm to be used for sorting the arrays.

  • ascending (bool, default=True) – Whether to sort in ascending order. Ignored when arrays have ndim > 1.

Returns:

The indices that permute the rows into grouped order.

Return type:

pdarray

Raises:

ValueError – If the inputs are not all the same size or not valid array types.

See also

argsort

Notes

Uses a least-significant-digit radix sort, which is stable and resilient to non-uniformity in data but communication intensive. Starts with the last array and moves forward.

For Strings, sorting is based on a hash. This ensures grouping of identical strings, but not lexicographic order. For Categoricals, sorting is based on the internal codes.

Examples

>>> import arkouda as ak
>>> a = ak.array([0, 1, 0, 1])
>>> b = ak.array([1, 1, 0, 0])
>>> perm = ak.coargsort([a, b])
>>> perm
array([2 0 3 1])
>>> a[perm]
array([0 0 1 1])
>>> b[perm]
array([0 1 0 1])