Return change in -2LL in umxRun

R/build_run_modify.R

@@ -3785,7 +3785,6 @@ umxAlgebra <- function(name = NA, expression, dimnames = NA, ..., joinKey=as.cha
 #' 
 # type = c("Auto", "FIML", "cov", "cor", "WLS", "DWLS", "ULS"),
 umxRun <- function(model, tryHard = c( "yes", "no", "ordinal", "search"), calc_sat = TRUE, setValues = FALSE, setLabels = FALSE, summary = !umx_set_silent(silent = TRUE), intervals = FALSE, optimizer = NULL, comparison = NULL){
-	# TODO: umxRun: Return change in -2LL for models being re-run
 	# TODO: umxRun: Stash saturated model for re-use
 	# TODO: umxRun: Optimise for speed
 	tryHard    = match.arg(tryHard)
@@ -3803,8 +3802,25 @@ umxRun <- function(model, tryHard = c( "yes", "no", "ordinal", "search"), calc_s
 	if(setValues){
 		model = xmuValues(model)
 	}
+
+	# Check if the model has been run
+	start2LL = if(!is.null(model$output)) model$output$Minus2LogLikelihood else NULL
+
 	model = xmu_safe_run_summary(model, autoRun = TRUE,  summary = summary, tryHard =  tryHard)
 
+	if(!is.null(start2LL)){
+		# 1. Was run
+		# 2. Has a previous -2LL
+		end2LL = model$output$Minus2LogLikelihood
+		if(!is.null(end2LL)){
+			# 3. Has a new -2LL
+			model@output$changeLL = end2LL - start2LL
+			if(summary){
+				message("Change in -2LL = ", round(model@output$changeLL, 3))
+			}
+		}
+	}
+
 	if(calc_sat){
 		if(umx_is_RAM(model)){
 			if(model$data$type == "raw"){

repro_umxRun_change.R

@@ -0,0 +1,39 @@
+library(umx)
+data(demoOneFactor)
+latents  = c("G")
+manifests = names(demoOneFactor)
+m1 = mxModel("fact", type="RAM", manifestVars=manifests, latentVars=latents,
+	mxPath(latents  , to = manifests),
+	mxPath(manifests, arrows = 2),
+	mxPath(latents  , arrows = 2, free = FALSE, values = 1),
+	mxData(cov(demoOneFactor), type = "cov", numObs=500)
+)
+m1 = umxRun(m1)
+# Initial run, start2LL should be NULL, so no message about change.
+
+# Modify model to make it worse/better
+# umxModify calls xmu_safe_run_summary internally? Yes.
+# But let's use umxRun on a run model.
+m1_rerun = umxRun(m1)
+# Should see "Change in -2LL = 0" (or close to 0)
+
+# Modify manually to force a change
+m3 = m1
+m3$S$values[1,1] = 0.5 # Change start value
+m3 = umxRun(m3)
+# m3 has output from m1 (it is a copy). So start2LL is m1's fit.
+# New run will find optimum (which should be same as m1 if only start value changed and convex).
+# So change 0.
+
+# What if we fix a parameter?
+m4 = omxSetParameters(m1, labels="G_to_x1", free=FALSE, values=.1)
+# m4 still has m1's output? Yes, omxSetParameters preserves output slot?
+# Let's assume yes.
+m4 = umxRun(m4)
+# Should show large change.
+if(!is.null(m4$output$changeLL)){
+    message("Test passed: changeLL found in output")
+    print(m4$output$changeLL)
+} else {
+    message("Test failed: changeLL not found in output")
+}