ds_list_vmr

Wikipedia:

In probability theory and statistics, the variance-to-mean ratio (VMR), like the coefficient of variation, is a normalized measure of the dispersion of a probability distribution: it is a measure used to quantify whether a set of observed occurrences are clustered or dispersed compared to a standard statistical model.

It is defined as the ratio of the variance \(\sigma^2\) to the mean \(\mu\),

\( \large D = {\sigma^2 \over \mu } \).

ds_list_vmr(list, sample): Returns the variance-to-mean ratio of values in a list.

COPY/// @func   ds_list_vmr(list, sample)
///
/// @desc   Returns the variance-to-mean ratio of values in a list.
///         Computes for a sample or entire population (default).
///
/// @param  {list}      list        list data structure
/// @param  {bool}      sample      true for sample, false for population
///
/// @return {real}      variance-to-mean ratio
///
/// GMLscripts.com/license

function ds_list_vmr(list, sample=false)
{
    var n = ds_list_size(list);
    if (n == 0) return undefined;

    var avg = 0;
    var sum = 0;

    for (var i=0; i<n; i++) avg += ds_list_find_value(list, i);
    avg /= n;

    for (var i=0; i<n; i++) sum += sqr(ds_list_find_value(list, i) - avg);

    return sum / (n - real(sample)) / avg;
}

Contributors: Quimp

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