dask.array.select — Dask documentation (original) (raw)

dask.array.select¶

dask.array.select(condlist, choicelist, default=0)[source]¶

Return an array drawn from elements in choicelist, depending on conditions.

This docstring was copied from numpy.select.

Some inconsistencies with the Dask version may exist.

Parameters

condlistlist of bool ndarrays

The list of conditions which determine from which array in choicelistthe output elements are taken. When multiple conditions are satisfied, the first one encountered in condlist is used.

choicelistlist of ndarrays

The list of arrays from which the output elements are taken. It has to be of the same length as condlist.

defaultscalar, optional

The element inserted in output when all conditions evaluate to False.

Returns

outputndarray

The output at position m is the m-th element of the array inchoicelist where the m-th element of the corresponding array incondlist is True.

Examples

Beginning with an array of integers from 0 to 5 (inclusive), elements less than 3 are negated, elements greater than 3are squared, and elements not meeting either of these conditions (exactly 3) are replaced with a default value of 42.

x = np.arange(6)
condlist = [x<3, x>3]
choicelist = [x, x**2]
np.select(condlist, choicelist, 42)
array([ 0, 1, 2, 42, 16, 25])

When multiple conditions are satisfied, the first one encountered incondlist is used.

condlist = [x<=4, x>3]
choicelist = [x, x**2]
np.select(condlist, choicelist, 55)
array([ 0, 1, 2, 3, 4, 25])