Set Functions

Array API specification for creating and operating on sets.

A conforming implementation of the array API standard must provide and support the following functions adhering to the following conventions.

  • Positional parameters must be positional-only parameters. Positional-only parameters have no externally-usable name. When a function accepting positional-only parameters is called, positional arguments are mapped to these parameters based solely on their order.

  • Optional parameters must be keyword-only arguments.

  • Unless stated otherwise, functions must support the data types defined in Data Types .

Objects in API

unique(x, /, *, return_counts=False, return_index=False, return_inverse=False)

Returns the unique elements of an input array x .

Parameters

  • x : <array>

    • input array. If x has more than one dimension, the function must flatten x and return the unique elements of the flattened array.

  • return_counts : bool

    • If True , the function must also return the number of times each unique element occurs in x . Default: False .

  • return_index : bool

    • If True , the function must also return the indices (first occurrences) of x that result in the unique array. Default: False .

  • return_inverse : bool

    • If True , the function must also return the indices of the unique array that reconstruct x . Default: False .

Returns

  • out : Union[ <array>, Tuple[ <array>, … ] ]

    • if return_counts , return_index , and return_inverse are all False , an array containing the set of unique elements in x ; otherwise, a tuple containing two or more of the following arrays (in order):

      • unique : <array>

        • an array containing the set of unique elements in x . The returned array must have the same data type as x .

        Note

        The order of elements is not specified, and may vary between implementations.

      • indices : <array>

        • an array containing the indices (first occurrences) of x that result in unique . The returned array must have the default integer data type.

      • inverse : <array>

        • an array containing the indices of unique that reconstruct x . The returned array must have the default integer data type.

      • counts : <array>

        • an array containing the number of times each unique element occurs in x .

          TODO: should this be int64 ? This probably makes sense for most hardware; however, may be undesirable for older hardware and/or embedded systems.