Diagonal & Index Generators

diag_indices

Return the indices to access the main diagonal of an array with ndim dimensions.

function diag_indices(n: number, ndim?: number): NDArray[]

Name	Type	Default	Description
`n`	`number`	—	Size of the array along each dimension.
`ndim`	`number`	`2`	Number of dimensions.

Returns: NDArray[] — Tuple of ndim index arrays, each of length n, that together select the main diagonal.

import * as np from 'numpy-ts';

const [di, dj] = np.diag_indices(3);
// di: array([0, 1, 2])
// dj: array([0, 1, 2])

// Use to set the diagonal of a matrix
const a = np.zeros([3, 3]);
a.iset([di, dj], 1);
// array([[1, 0, 0],
//        [0, 1, 0],
//        [0, 0, 1]])

diag_indices_from

Return the indices to access the main diagonal of a given array.

function diag_indices_from(a: ArrayLike): NDArray[]

Name	Type	Default	Description
`a`	`ArrayLike`	—	Array whose diagonal indices are desired. Must be at least 2-D and have equal-length dimensions.

Returns: NDArray[] — Tuple of index arrays that select the main diagonal of arr.

import * as np from 'numpy-ts';

const a = np.eye(4);
const [di, dj] = np.diag_indices_from(a);
// di: array([0, 1, 2, 3])
// dj: array([0, 1, 2, 3])

tril_indices

Return the indices for the lower triangle of an (n, m) array.

function tril_indices(n: number, k?: number, m?: number): NDArray[]

Name	Type	Default	Description
`n`	`number`	—	Number of rows in the array.
`k`	`number`	`0`	Diagonal offset. `k=0` is the main diagonal, `k<0` is below it, `k>0` is above it.
`m`	`number`	`n`	Number of columns. Defaults to `n` (square array).

Returns: [NDArray, NDArray] — Row and column index arrays for the lower triangle.

import * as np from 'numpy-ts';

const [rows, cols] = np.tril_indices(3);
// rows: array([0, 1, 1, 2, 2, 2])
// cols: array([0, 0, 1, 0, 1, 2])

// Include one diagonal above the main
const [r, c] = np.tril_indices(3, 1);
// r: array([0, 0, 1, 1, 1, 2, 2, 2])
// c: array([0, 1, 0, 1, 2, 0, 1, 2])

tril_indices_from

Return the indices for the lower triangle of a given array.

function tril_indices_from(a: ArrayLike, k?: number): NDArray[]

Name	Type	Default	Description
`a`	`ArrayLike`	—	Input array. Must be at least 2-D. Uses the last two dimensions to determine the triangle.
`k`	`number`	`0`	Diagonal offset.

Returns: [NDArray, NDArray] — Row and column index arrays for the lower triangle.

import * as np from 'numpy-ts';

const a = np.ones([3, 4]);
const [rows, cols] = np.tril_indices_from(a);
// rows: array([0, 1, 1, 2, 2, 2])
// cols: array([0, 0, 1, 0, 1, 2])

triu_indices

Return the indices for the upper triangle of an (n, m) array.

function triu_indices(n: number, k?: number, m?: number): NDArray[]

Name	Type	Default	Description
`n`	`number`	—	Number of rows in the array.
`k`	`number`	`0`	Diagonal offset. `k=0` is the main diagonal, `k<0` is below it, `k>0` is above it.
`m`	`number`	`n`	Number of columns. Defaults to `n` (square array).

Returns: [NDArray, NDArray] — Row and column index arrays for the upper triangle.

import * as np from 'numpy-ts';

const [rows, cols] = np.triu_indices(3);
// rows: array([0, 0, 0, 1, 1, 2])
// cols: array([0, 1, 2, 1, 2, 2])

// Exclude the main diagonal
const [r, c] = np.triu_indices(3, 1);
// r: array([0, 0, 1])
// c: array([1, 2, 2])

triu_indices_from

Return the indices for the upper triangle of a given array.

function triu_indices_from(a: ArrayLike, k?: number): NDArray[]

Name	Type	Default	Description
`a`	`ArrayLike`	—	Input array. Must be at least 2-D. Uses the last two dimensions to determine the triangle.
`k`	`number`	`0`	Diagonal offset.

Returns: [NDArray, NDArray] — Row and column index arrays for the upper triangle.

import * as np from 'numpy-ts';

const a = np.ones([4, 4]);
const [rows, cols] = np.triu_indices_from(a);
// rows: array([0, 0, 0, 0, 1, 1, 1, 2, 2, 3])
// cols: array([0, 1, 2, 3, 1, 2, 3, 2, 3, 3])

mask_indices

Return the indices to access an (n, n) array given a masking function.

function mask_indices(
  n: number,
  mask_func: (n: number, k?: number) => NDArray,
  k?: number
): NDArray[]

Name	Type	Default	Description
`n`	`number`	—	Size of the square array.
`mask_func`	`(n: number, k?: number) => NDArray`	—	A function that accepts `(n, k)` and returns a 2-D boolean or integer array (like `triu` or `tril`).
`k`	`number`	`0`	Optional diagonal offset passed to `mask_func`.

Returns: [NDArray, NDArray] — Row and column index arrays where mask_func returns non-zero values.

import * as np from 'numpy-ts';

// Get indices of upper triangle (excluding diagonal)
const [rows, cols] = np.mask_indices(3, np.triu, 1);
// rows: array([0, 0, 1])
// cols: array([1, 2, 2])

indices

Return an array representing the indices of a grid.

function indices(
  dimensions: number[],
  dtype?: DType
): NDArray

Name	Type	Default	Description
`dimensions`	`number[]`	—	Shape of the grid.
`dtype`	`DType`	`'float64'`	Data type of the result. As of v1.3.0, integer-index APIs default to `float64` to avoid `BigInt` interop friction (NumPy uses `int64`).

Returns: NDArray dense grid with shape [N, ...dimensions].

import * as np from 'numpy-ts';

const grid = np.indices([2, 3]);
// grid[0]: array([[0, 0, 0], [1, 1, 1]])  -- row indices
// grid[1]: array([[0, 1, 2], [0, 1, 2]])  -- column indices

ix_

Construct an open mesh from multiple sequences. This is useful for constructing index arrays for cross-indexing.

function ix_(...args: ArrayLike[]): NDArray[]

Name	Type	Default	Description
`...args`	`ArrayLike[]`	—	1-D sequences. Each sequence is reshaped so that it broadcasts against the others.

Returns: NDArray[] — Tuple of N-D arrays with shapes (len(a0), 1, ..., 1), (1, len(a1), 1, ..., 1), etc.

import * as np from 'numpy-ts';

const [iy, ix] = np.ix_([0, 2], [1, 3]);
// iy: array([[0], [2]])   -- shape [2, 1]
// ix: array([[1, 3]])     -- shape [1, 2]

// Use for cross-indexing a 4x4 matrix
const a = np.arange(16).reshape([4, 4]);
// Select rows 0,2 and columns 1,3

fill_diagonal

Fill the main diagonal of the given array in-place.

function fill_diagonal(a: NDArray, val: number, wrap?: boolean): void

Name	Type	Default	Description
`a`	`NDArray`	—	Array to modify. Must be at least 2-D.
`val`	`number \| ArrayLike`	—	Value(s) to write on the diagonal. If an array, values are repeated cyclically to fill the entire diagonal.
`wrap`	`boolean`	`false`	For tall matrices (rows > cols), if `true`, the diagonal wraps after reaching the last column.

Returns: void — The array a is modified in-place.

import * as np from 'numpy-ts';

const a = np.zeros([3, 3]);
np.fill_diagonal(a, 5);
// array([[5, 0, 0],
//        [0, 5, 0],
//        [0, 0, 5]])

const b = np.zeros([3, 3]);
np.fill_diagonal(b, [1, 2, 3]);
// array([[1, 0, 0],
//        [0, 2, 0],
//        [0, 0, 3]])

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Diagonal & Index Generators

diag_indices

diag_indices_from

tril_indices

tril_indices_from

triu_indices

triu_indices_from

mask_indices

indices

ix_

fill_diagonal

​diag_indices

​diag_indices_from

​tril_indices

​tril_indices_from

​triu_indices

​triu_indices_from

​mask_indices

​indices

​ix_

​fill_diagonal

diag_indices

diag_indices_from

tril_indices

tril_indices_from

triu_indices

triu_indices_from

mask_indices

indices

ix_

fill_diagonal