replace fitlog with a column table, always populate it

[palday]

• add entry in NEWS.md

closes #618

[codecov]

Codecov Report

❌ Patch coverage is 97.14286% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.51%. Comparing base (bf4b8eb) to head (1034335).
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Files with missing lines	Patch %	Lines
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[dmbates]

@palday I had an alternative approach using a "matrix table" for the result, as defined in Tables.jl. Because the objective is Float64 and the theta value is Vector{Float64} (or T and Vector{T} where {T}, if you prefer) we can push! the objective and merge! the theta value onto the end of a Vector{T}. At convergence we apply Tables.table to the transpose of a reshape of this vector into a matrix of size (ntheta + 1, neval). We need to have names for the columns (after transposing) and I generated them from the parmap, as in par_1_1_1. Is it okay with you if I make such a change? We can back it out later if it doesn't seem to be working.

[palday]

@dmbates please go ahead!

[dmbates]

As I said in the review of #853 I think my plan of creating a MatrixTable for the fitlog led to too many changes so I think that this PR and #853 should both be merged. Afterwards I will add an extractor function to create a table with scalar columns from the current tabular form, in case that is desired.

[palday]

Afterwards I will add an extractor function to create a table with scalar columns from the current tabular form, in case that is desired.

@dmbates don't forget that we have a Tables.columntable method that does something similar:

MixedModels.jl/src/optsummary.jl

Lines 108 to 134 in bf4b8eb

	"""
	columntable(s::OptSummary, [stack::Bool=false])
	Return `s.fitlog` as a `Tables.columntable`.
	When `stack` is false (the default), there will be 3 columns in the result:
	- `iter`: the iteration number
	- `objective`: the value of the objective at that sample
	- `θ`: the parameter vector at that sample
	When `stack` is true, there will be 4 columns: `iter`, `objective`, `par`, and `value`
	where `value` is the stacked contents of the `θ` vectors (the equivalent of `vcat(θ...)`)
	and `par` is a vector of parameter numbers.
	"""
	function Tables.columntable(s::OptSummary; stack::Bool=false)
	fitlog = s.fitlog
	val = (; iter=axes(fitlog, 1), objective=last.(fitlog), θ=first.(fitlog))
	stack || return val
	θ1 = first(val.θ)
	k = length(θ1)
	return (;
	iter=repeat(val.iter; inner=k),
	objective=repeat(val.objective; inner=k),
	par=repeat(1:k; outer=length(fitlog)),
	value=foldl(vcat, val.θ; init=(eltype(θ1))[]),
	)
	end