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nancumin

Calculate the cumulative minimum of a strided array, ignoring NaN values.

Usage

var nancumin = require( '@stdlib/stats/strided/nancumin' );

nancumin( N, x, strideX, y, strideY )

Computes the cumulative minimum of a strided array x, ignoring NaN values.

var x = [ 1.0, -2.0, NaN, 2.0 ];
var y = [ 0.0, 0.0, 0.0, 0.0 ];

var v = nancumin( x.length, x, 1, y, 1 );
// returns [ 1.0, -2.0, -2.0, -2.0 ]

The function has the following parameters:

The N and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to compute the cumulative minimum of every other element in x,

var x = [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0, NaN, NaN ];
var y = [ 0.0, 0.0, 0.0, 0.0, 0.0 ];

var v = nancumin( 5, x, 2, y, 1 );
// returns [ 1.0, 1.0, -2.0, -2.0, -2.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float64Array = require( '@stdlib/array/float64' );

var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, NaN, NaN, 4.0 ] );
var y0 = new Float64Array( 4 );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 );
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*0 );

var v = nancumin( 4, x1, 2, y1, 1 );
// returns <Float64Array>[ 1.0, -2.0, -2.0, -2.0 ]

nancumin.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )

Computes the cumulative minimum of a strided array, ignoring NaN values and using alternative indexing semantics.

var x = [ 1.0, -2.0, NaN, 2.0 ];
var y = [ 0.0, 0.0, 0.0, 0.0 ];

var v = nancumin.ndarray( x.length, x, 1, 0, y, 1, 0 );
// returns [ 1.0, -2.0, -2.0, -2.0 ]

The function has the following additional parameters:

  • offsetX: starting index for x.
  • offsetY: starting index for y.

While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on a starting index. For example, to calculate the cumulative minimum for every other element in x starting from the second element

var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, NaN, NaN, 2.0, 3.0, 4.0 ];
var y = [ 0.0, 0.0, 0.0, 0.0, 0.0 ];

var v = nancumin.ndarray( 5, x, 2, 1, y, 1, 0 );
// returns [ 1.0, -2.0, -2.0, -2.0, -2.0 ]

Notes

  • If N <= 0, both functions return the output array unchanged.
  • Both functions support array-like objects having getter and setter accessors for array element access (e.g., @stdlib/array/base/accessor).

Examples

var uniform = require( '@stdlib/random/base/uniform' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var bernoulli = require( '@stdlib/random/base/bernoulli' );
var zeros = require( '@stdlib/array/zeros' );
var nancumin = require( '@stdlib/stats/strided/nancumin' );

function rand() {
    if ( bernoulli( 0.8 ) < 1 ) {
        return NaN;
    }
    return uniform( -50.0, 50.0 );
}

var x = filledarrayBy( 10, 'float64', rand );
console.log( x );

var y = zeros( 10, 'float64' );
console.log( y );

var v = nancumin( x.length, x, 1, y, 1 );
console.log( v );