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where

Return elements chosen from x or y depending on a condition. When called with only a condition, returns the indices of non-zero elements (equivalent to nonzero). 
function where(condition: ArrayLike, x?: ArrayLike, y?: ArrayLike): NDArray | NDArray[]
NameTypeDefaultDescription
conditionArrayLike—Boolean or numeric array. Where true (non-zero), yield x; otherwise yield y.
xArrayLikeundefinedValues where condition is true. Required if y is provided.
yArrayLikeundefinedValues where condition is false. Required if x is provided.
Returns: NDArray when x and y are given (array of chosen elements). NDArray[] when only condition is given (tuple of index arrays, one per dimension). 
import * as np from 'numpy-ts';

// Three-argument form: choose from x or y
const a = np.array([1, 2, 3, 4, 5]);
const result = np.where(np.greater(a, 3), a, np.zeros([5]));
// array([0, 0, 0, 4, 5])

// One-argument form: return indices of non-zero elements
const indices = np.where(np.array([0, 1, 0, 1, 1]));
// [array([1, 3, 4])]

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nonzero

Return the indices of non-zero elements. For an N-dimensional array, returns a tuple of N arrays, one for each dimension. 
function nonzero(a: ArrayLike): NDArray[]
NameTypeDefaultDescription
aArrayLike—Input array.
Returns: NDArray[] — Tuple of arrays, one per dimension, containing the indices of non-zero elements. 
import * as np from 'numpy-ts';

const a = np.array([0, 1, 0, 3, 0]);
const [indices] = np.nonzero(a);
// indices = array([1, 3])

// 2D example
const b = np.array([[1, 0], [0, 2]]);
const [rows, cols] = np.nonzero(b);
// rows = array([0, 1])
// cols = array([0, 1])

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argwhere

Find the indices of non-zero elements, returned as a 2D array where each row is the index tuple of a non-zero element. 
function argwhere(a: ArrayLike): NDArray
NameTypeDefaultDescription
aArrayLike—Input array.
Returns: NDArray — 2D array of shape (N, a.ndim) where N is the number of non-zero elements. Each row is the multi-dimensional index of a non-zero element. 
import * as np from 'numpy-ts';

const a = np.array([[1, 0], [0, 2]]);
const result = np.argwhere(a);
// array([[0, 0],
//        [1, 1]])

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flatnonzero

Return indices of non-zero elements in the flattened version of the array. 
function flatnonzero(a: ArrayLike): NDArray
NameTypeDefaultDescription
aArrayLike—Input array.
Returns: NDArray — 1D array of indices into the flattened array where elements are non-zero. 
import * as np from 'numpy-ts';

const a = np.array([[0, 1], [2, 0]]);
const result = np.flatnonzero(a);
// array([1, 2])
// (index 1 = element 1, index 2 = element 2 in flattened [0,1,2,0])

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searchsorted

Find indices where elements should be inserted to maintain sorted order. The input array a must be sorted in ascending order. 
function searchsorted(a: ArrayLike, v: ArrayLike, side?: 'left' | 'right'): NDArray
NameTypeDefaultDescription
aArrayLike—Sorted 1D input array.
vArrayLike—Values to insert.
side'left' | 'right''left'If 'left', the index of the first suitable location is returned. If 'right', the last suitable location is returned.
Returns: NDArray — Indices of insertion points. 
import * as np from 'numpy-ts';

const a = np.array([1, 2, 3, 4, 5]);

np.searchsorted(a, 3);
// 2 (insert before index 2 to keep sorted)

np.searchsorted(a, 3, 'right');
// 3 (insert after existing 3)

np.searchsorted(a, [0, 3, 6]);
// array([0, 2, 5])

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extract

Return elements of an array where a condition is true. Equivalent to a[condition] on the flattened array. 
function extract(condition: ArrayLike, a: ArrayLike): NDArray
NameTypeDefaultDescription
conditionArrayLike—Boolean array. Must be broadcastable to the shape of a.
aArrayLike—Input array.
Returns: NDArray — 1D array of elements from a where condition is true. 
import * as np from 'numpy-ts';

const a = np.array([10, 20, 30, 40, 50]);
const condition = np.array([true, false, true, false, true]);

const result = np.extract(condition, a);
// array([10, 30, 50])

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count_nonzero

Count the number of non-zero elements in the array. 
function count_nonzero(a: ArrayLike, axis?: number): number | NDArray
NameTypeDefaultDescription
aArrayLike—Input array.
axisnumberundefinedAxis along which to count. If undefined, counts over the entire array.
Returns: number when no axis is specified. NDArray when counting along specific axes. 
import * as np from 'numpy-ts';

const a = np.array([[0, 1, 2], [3, 0, 0]]);

np.count_nonzero(a);
// 3

np.count_nonzero(a, 0);
// array([1, 1, 1])

np.count_nonzero(a, 1);
// array([2, 1])