cupynumeric.choose#

cupynumeric.choose( a: ndarray, choices: Sequence[ndarray], out: ndarray | None = None, mode: BoundsMode = 'raise', ) → ndarray#

Construct an array from an index array and a list of arrays to choose from.

Given an “index” array (a) of integers and a sequence of n arrays (choices), a and each choice array are first broadcast, as necessary, to arrays of a common shape; calling these Ba and Bchoices[i], i = 0,…,n-1 we have that, necessarily, Ba.shape == Bchoices[i].shape for each i. Then, a new array with shape Ba.shape is created as follows:

if mode='raise' (the default), then, first of all, each element of a (and thus Ba) must be in the range [0, n-1]; now, suppose that i (in that range) is the value at the (j0, j1, ..., jm) position in Ba - then the value at the same position in the new array is the value in Bchoices[i] at that same position;
if mode='wrap', values in a (and thus Ba) may be any (signed) integer; modular arithmetic is used to map integers outside the range [0, n-1] back into that range; and then the new array is constructed as above;
if mode='clip', values in a (and thus Ba) may be any (signed) integer; negative integers are mapped to 0; values greater than n-1 are mapped to n-1; and then the new array is constructed as above.

Parameters:

a (ndarray[int]) – This array must contain integers in [0, n-1], where n is the number of choices, unless mode=wrap or mode=clip, in which cases any integers are permissible.
choices (Sequence[ndarray]) – Choice arrays. a and all of the choices must be broadcastable to the same shape. If choices is itself an array (not recommended), then its outermost dimension (i.e., the one corresponding to choices.shape[0]) is taken as defining the “sequence”.
out (ndarray, optional) – If provided, the result will be inserted into this array. It should be of the appropriate shape and dtype. Note that out is always buffered if mode='raise'; use other modes for better performance.
mode ({'raise', 'wrap', 'clip'}, optional) –
Specifies how indices outside [0, n-1] will be treated:
- ’raise’ : an exception is raised (default)
- ’wrap’ : value becomes value mod n
- ’clip’ : values < 0 are mapped to 0, values > n-1 are mapped to n-1

Returns:

merged_array – The merged result.

Return type:

ndarray

Raises:

ValueError – shape mismatch: If a and each choice array are not all broadcastable to the same shape.