update multi-group correction

deduplicate the correction scale methods and move to Sem.jl

Author: Alexey Stukalov

src/additional_functions/helper.jl

@@ -115,8 +115,3 @@ function nonunique(values::AbstractVector)
     end
     return res
 end
-
-# scaling corrections for multigroup models
-mg_correction(::SemFIML) = 0
-mg_correction(::SemML) = 0
-mg_correction(::SemWLS) = -1

src/frontend/fit/fitmeasures/RMSEA.jl

@@ -21,14 +21,9 @@ For multigroup models, the correction proposed by J.H. Steiger is applied
 """
 RMSEA(fit::SemFit) = RMSEA(fit, fit.model)
 
-# scaling corrections
-RMSEA_corr_scale(::Type{<:SemFIML}) = 0
-RMSEA_corr_scale(::Type{<:SemML}) = -1
-RMSEA_corr_scale(::Type{<:SemWLS}) = -1
-
 function RMSEA(fit::SemFit, model::AbstractSem)
     term_type = check_same_semterm_type(model; throw_error = true)
-    n = nsamples(fit) + nsem_terms(model) * RMSEA_corr_scale(term_type)
+    n = nsamples(fit) + nsem_terms(model) * multigroup_correction_scale(term_type)
     sqrt(nsem_terms(model)) * RMSEA(dof(fit), χ²(fit), n)
 end
 

src/frontend/specification/Sem.jl

@@ -45,32 +45,47 @@ function Base.show(io::IO, term::LossTerm)
     end
 end
 
-############################################################################################
-# constructor for Sem types
-############################################################################################
+# scaling corrections for multigroup models
+
+# fallback method for non-standard SemLoss type
+multigroup_correction_scale(::Type{<:SemLoss}) = nothing
 
-function multigroup_weights(models, n)
-    nsamples_total = sum(nsamples, models)
+multigroup_correction_scale(::Type{<:SemFIML}) = 0
+multigroup_correction_scale(::Type{<:SemML}) = 0
+multigroup_correction_scale(::Type{<:SemWLS}) = -1
+
+multigroup_correction_scale(loss::SemLoss) =
+    multigroup_correction_scale(typeof(loss))
+
+# calculate sem term weights for multigroup models
+# correcting for the number of samples and the loss type
+function multigroup_weights(semterms...)
+    n = length(semterms)
+    nsamples_total = sum(nsamples, semterms)
     semloss_type = check_same_semterm_type(semterms; throw_error = false)
     if isnothing(semloss_type)
         @info """
         Your ensemble model contains heterogeneous loss functions.
         Default weights of (#samples per group/#total samples) will be used
         """
-        return [(nsamples(model)) / (nsamples_total) for model in models]
-    end
-    lossfun = models[1].loss.functions[1]
-    if !applicable(mg_correction, lossfun)
-        @info """
-        We don't know how to choose group weights for the specified loss function.
-        Default weights of (#samples per group/#total samples) will be used
-        """
-        return [(nsamples(model)) / (nsamples_total) for model in models]
+        c = 0
+    else
+        c = multigroup_correction_scale(semloss_type)
+        if isnothing(c)
+            @info """
+            We don't know how to choose group weights for the specified loss function.
+            Default weights of (#samples per group/#total samples) will be used
+            """
+            c = 0
+        end
     end
-    c = mg_correction(lossfun)
-    return [(nsamples(model)+c) / (nsamples_total+n*c) for model in models]
+    return [(nsamples(term)+c) / (nsamples_total+n*c) for term in semterms]
 end
 
+############################################################################################
+# constructor for Sem types
+############################################################################################
+
 function Sem(
     loss_terms...;
     params::Union{Vector{Symbol}, Nothing} = nothing,