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README.md

incrnanhmean

Compute a harmonic mean incrementally, ignoring NaN values.

The harmonic mean of positive real numbers x_0, x_1, ..., x_{n-1} is defined as

$$\begin{align}H &= \frac{n}{\frac{1}{x_0} + \frac{1}{x_1} + \cdots + \frac{1}{x_{n-1}}} \\ &= \frac{\displaystyle n}{\displaystyle\sum_{i=0}^{n-1} \frac{1}{x_i}} \\ &= \biggl( \frac{\displaystyle\sum_{i=0}^{n-1} \frac{1}{x_i}}{\displaystyle n} \biggr)^{-1}\end{align}$$

Usage

var incrnanhmean = require( '@stdlib/stats/incr/nanhmean' );

incrnanhmean()

Returns an accumulator function which incrementally computes a harmonic mean, ignoring NaN values.

var accumulator = incrnanhmean();

accumulator( [x] )

If provided an input value x, the accumulator function returns an updated harmonic mean. If not provided an input value x, the accumulator function returns the current harmonic mean.

var accumulator = incrnanhmean();

var v = accumulator( 2.0 );
// returns 2.0

v = accumulator( 1.0 );
// returns ~1.33

v = accumulator( NaN );
// returns ~1.33

v = accumulator( 3.0 );
// returns ~1.64

v = accumulator();
// returns ~1.64

Notes

  • Input values are not type checked. If non-numeric inputs are possible, you are advised to type check and handle accordingly before passing the value to the accumulator function.

Examples

var uniform = require( '@stdlib/random/base/uniform' );
var bernoulli = require( '@stdlib/random/base/bernoulli' );
var incrnanhmean = require( '@stdlib/stats/incr/nanhmean' );

var accumulator;
var v;
var i;

// Initialize an accumulator:
accumulator = incrnanhmean();

// For each simulated datum, update the harmonic mean...
for ( i = 0; i < 100; i++ ) {
    if ( bernoulli( 0.2 ) ) {
        v = NaN;
    } else {
        v = uniform( 1.0, 100.0 );
    }
    accumulator( v );
}
console.log( accumulator() );