var indexOf = require( '@stdlib/blas/ext/index-of' );

Returns the first index of a specified search element along an ndarray dimension.

var array = require( '@stdlib/ndarray/array' );

// Create an input ndarray:
var x = array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
// returns <ndarray>

// Perform operation:
var out = indexOf( x, 2.0 );
// returns <ndarray>

var idx = out.get();
// returns 1

The function has the following parameters:

• x: input ndarray. Must have at least one dimension.
• searchElement: search element. May be either a scalar value or an ndarray. If provided a scalar value, the value is cast to the data type of the input ndarray. If provided an ndarray, the value must have a shape which is broadcast-compatible with the non-reduced dimensions of the input ndarray. For example, given the input shape [2, 3, 4] and options.dim=0, the search element ndarray must have a shape which is broadcast-compatible with the shape [3, 4].
• fromIndex: index from which to begin searching (optional). May be either a scalar value or an ndarray having an integer index or "generic" data type. If provided an ndarray, the value must have a shape which is broadcast-compatible with the non-reduced dimensions of the input ndarray. For example, given the input shape [2, 3, 4] and options.dim=0, a provided ndarray must have a shape which is broadcast-compatible with the shape [3, 4]. If provided a negative integer, the index at which to begin searching along a dimension is determined by counting backward from the last element (where -1 refers to the last element). Default: 0.
• options: function options (optional).

The function accepts the following options:

• dtype: output ndarray data type. Must be an integer index or generic data type.
• dim: dimension over which to perform operation. If provided a negative integer, the dimension along which to perform the operation is determined by counting backward from the last dimension (where -1 refers to the last dimension). Default: -1.
• keepdims: boolean indicating whether the reduced dimensions should be included in the returned ndarray as singleton dimensions. Default: false.

If the function is unable to find a search element along an ndarray, the corresponding element in the returned ndarray is -1.

var array = require( '@stdlib/ndarray/array' );

// Create an input ndarray:
var x = array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
// returns <ndarray>

// Perform operation:
var out = indexOf( x, 10.0 );
// returns <ndarray>

var idx = out.get();
// returns -1

By default, the function begins searching from the first element along the reduction dimension. To begin searching from a different index, provide a fromIndex argument.

var array = require( '@stdlib/ndarray/array' );

// Create an input ndarray:
var x = array( [ 1.0, 2.0, 3.0, 4.0, 2.0, 6.0 ] );
// returns <ndarray>

// Perform operation:
var out = indexOf( x, 2.0, 2 );
// returns <ndarray>

var idx = out.get();
// returns 4

By default, the function performs the operation over elements in the last dimension. To perform the operation over a different dimension, provide a dim option.

var ndarray2array = require( '@stdlib/ndarray/to-array' );
var array = require( '@stdlib/ndarray/array' );

var x = array( [ [ -1.0, 2.0 ], [ -3.0, 4.0 ] ] );

var out = indexOf( x, -3.0, {
    'dim': 0
});
// returns <ndarray>

var idx = ndarray2array( out );
// returns [ 1, -1 ]

By default, the function excludes reduced dimensions from the output ndarray. To include the reduced dimensions as singleton dimensions, set the keepdims option to true.

var array = require( '@stdlib/ndarray/array' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );

var x = array( [ [ -1.0, 2.0 ], [ -3.0, 4.0 ] ] );

var opts = {
    'dim': 0,
    'keepdims': true
};

var out = indexOf( x, -3.0, opts );
// returns <ndarray>

var idx = ndarray2array( out );
// returns [ [ 1, -1 ] ]

By default, the function returns an ndarray having a data type determined by the function's output data type policy. To override the default behavior, set the dtype option.

var ndarray2array = require( '@stdlib/ndarray/to-array' );
var dtype = require( '@stdlib/ndarray/dtype' );
var array = require( '@stdlib/ndarray/array' );

var x = array( [ 1.0, 2.0, 3.0, 4.0 ] );

var idx = indexOf( x, 2.0, {
    'dtype': 'generic'
});
// returns <ndarray>

var dt = dtype( idx );
// returns 'generic'

Returns the first index of a specified search element along an ndarray dimension and assigns results to a provided output ndarray.

var array = require( '@stdlib/ndarray/array' );
var zeros = require( '@stdlib/ndarray/zeros' );

var x = array( [ 1.0, 2.0, 3.0, 4.0 ] );
var y = zeros( [], {
    'dtype': 'int32'
});

var out = indexOf.assign( x, 3.0, y );
// returns <ndarray>

var idx = out.get();
// returns 2

var bool = ( out === y );
// returns true

The method has the following parameters:

• x: input ndarray. Must have at least one dimension.
• searchElement: search element. May be either a scalar value or an ndarray. If provided a scalar value, the value is cast to the data type of the input ndarray. If provided an ndarray, the value must have a shape which is broadcast-compatible with the non-reduced dimensions of the input ndarray. For example, given the input shape [2, 3, 4] and options.dim=0, the search element ndarray must have a shape which is broadcast-compatible with the shape [3, 4].
• fromIndex: index from which to begin searching (optional). May be either a scalar value or an ndarray having an integer index or "generic" data type. If provided an ndarray, the value must have a shape which is broadcast-compatible with the non-reduced dimensions of the input ndarray. For example, given the input shape [2, 3, 4] and options.dim=0, a provided ndarray must have a shape which is broadcast-compatible with the shape [3, 4]. If provided a negative integer, the index at which to begin searching along a dimension is determined by counting backward from the last element (where -1 refers to the last element). Default: 0.
• out: output ndarray.
• options: function options (optional).

The method accepts the following options:

• dim: dimension over which to perform operation. If provided a negative integer, the dimension along which to perform the operation is determined by counting backward from the last dimension (where -1 refers to the last dimension). Default: -1.

• Setting the keepdims option to true can be useful when wanting to ensure that the output ndarray is broadcast-compatible with ndarrays having the same shape as the input ndarray.
• The output data type policy only applies to the main function and specifies that, by default, the function must return an ndarray having an integer index or "generic" data type. For the assign method, the output ndarray is allowed to have any supported output data type.