README.md

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OnlineStatsBase

This package defines the basic types and interface for OnlineStats.

Interface

Required

• _fit!(stat, y): Update the "sufficient statistics" of the estimator from a single observation y.

Optional

• _merge!(stat1, stat2) Merge stat2 into stat1. By default, a warning will occur.

Defaults

• value(stat, args...; kw...): Calculate the value of the estimator from the "sufficient statistics". By default, this returns the first field of the OnlineStat.
• nobs(stat): Return the number of observations. By default, this returns stat.n.

Example

• Make a subtype of OnlineStat and give it a _fit!(::OnlineStat{T}, y::T) method.
• T is the type of a single observation. Make sure it's adequately wide.

using OnlineStatsBase

mutable struct MyMean <: OnlineStat{Number}
    value::Float64
    n::Int
    MyMean() = new(0.0, 0)
end
function OnlineStatsBase._fit!(o::MyMean, y)
    o.n += 1
    o.value += (1 / o.n) * (y - o.value)
end

That's all there is to it!

y = randn(1000)

o = fit!(MyMean(), y)