The function `lt` in `OrdinalPatternEncoding` isn't actually used

[kahaaga]

The OrdinalPatterns documentation string promises that the user can provide a comparator function (defaults to lt = isless) to determine how two elements of a state are deemed to be "equal" (useful to prevent bias when there are tied values).

This function lt gets stored in the encoding::OrdinalPatternEncoding field of the OrdinalPatterns struct. However, the function isn't actually used in encode. We did use it before, but after we transitioned to the formal encode/decode interface, we forgot to pass the argument on to the underlying sortperm! call.

The fix is easy. Here's the source code:

function encode(encoding::OrdinalPatternEncoding{m}, χ::AbstractVector) where {m}
    if m != length(χ)
        throw(ArgumentError("Permutation order and length of input must match!"))
    end
    perm = sortperm!(encoding.perm, χ)
    return permutation_to_integer(perm)
end

TODO:

• [ ] Pass on lt to sortperm! when computing the permutation pattern.

[Datseris]

We should add a simple test for this case, like for the permutation entropy of ones(1000); one would give 0 (the one with isless) while the other one would give maximum (with the random comparison).