time-to-botec/js/node_modules/@stdlib/stats/incr/mmean/lib/main.js
NunoSempere b6addc7f05 feat: add the node modules
Necessary in order to clearly see the squiggle hotwiring.
2022-12-03 12:44:49 +00:00

136 lines
3.2 KiB
JavaScript

/**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var Float64Array = require( '@stdlib/array/float64' );
// MAIN //
/**
* Returns an accumulator function which incrementally computes a moving arithmetic mean.
*
* @param {PositiveInteger} W - window size
* @throws {TypeError} must provide a positive integer
* @returns {Function} accumulator function
*
* @example
* var accumulator = incrmmean( 3 );
*
* var mu = accumulator();
* // returns null
*
* mu = accumulator( 2.0 );
* // returns 2.0
*
* mu = accumulator( -5.0 );
* // returns -1.5
*
* mu = accumulator( 3.0 );
* // returns 0.0
*
* mu = accumulator( 5.0 );
* // returns 1.0
*
* mu = accumulator();
* // returns 1.0
*/
function incrmmean( W ) {
var delta;
var buf;
var mu;
var N;
var i;
if ( !isPositiveInteger( W ) ) {
throw new TypeError( 'invalid argument. Must provide a positive integer. Value: `' + W + '`.' );
}
buf = new Float64Array( W );
mu = 0.0;
i = -1;
N = 0;
return accumulator;
/**
* If provided a value, the accumulator function returns an updated mean. If not provided a value, the accumulator function returns the current mean.
*
* @private
* @param {number} [x] - input value
* @returns {(number|null)} mean or null
*/
function accumulator( x ) {
var k;
if ( arguments.length === 0 ) {
if ( N === 0 ) {
return null;
}
return mu;
}
// Update the index for managing the circular buffer:
i = (i+1) % W;
// Case: incoming value is NaN, the sliding mean is automatically NaN...
if ( isnan( x ) ) {
N = W; // explicitly set to avoid `N < W` branch
mu = NaN;
}
// Case: initial window...
else if ( N < W ) {
N += 1;
delta = x - mu;
mu += delta / N;
}
// Case: outgoing value is NaN, and, thus, we need to compute the sample mean...
else if ( isnan( buf[ i ] ) ) {
N = 1;
mu = x;
for ( k = 0; k < W; k++ ) {
if ( k !== i ) {
if ( isnan( buf[ k ] ) ) {
N = W; // explicitly set to avoid `N < W` branch
mu = NaN;
break; // mean is automatically NaN, so no need to continue
}
N += 1;
delta = buf[ k ] - mu;
mu += delta / N;
}
}
}
// Case: neither the current mean nor the incoming value are NaN, so we need to update the sample mean...
else if ( isnan( mu ) === false ) {
delta = x - buf[ i ];
mu += delta / W;
}
// Case: the current mean is NaN, so nothing to do until the buffer no longer contains NaN values...
buf[ i ] = x;
return mu;
}
}
// EXPORTS //
module.exports = incrmmean;