Plot the natural curve for extrapolation also in the negative quadrant

NEWS.Rmd

@@ -183,6 +183,10 @@ speed boost. The default setting can be overridden via the `rprime` argument
 use to find a good starting point failed: in such cases, we try again using
 the simulated fit (#549, fixed in #500; thanks to @SalOehl for reporting and
 providing data to reproduce the error).
+* The natural/simulated curve was not plotted in the negative quadrant for
+`mode = "extrapolation"`, which made it harder to see where it extrapolated
+to (#551, fixed in #552; thanks to @SalOehl for reporting).
+
 
 ### `calc_IEU()`
 * The code of this function has been consolidated to avoid duplication and

NEWS.md

@@ -214,6 +214,10 @@
   model we use to find a good starting point failed: in such cases, we
   try again using the simulated fit (#549, fixed in \#500; thanks to
   @SalOehl for reporting and providing data to reproduce the error).
+- The natural/simulated curve was not plotted in the negative quadrant
+  for `mode = "extrapolation"`, which made it harder to see where it
+  extrapolated to (#551, fixed in \#552; thanks to @SalOehl for
+  reporting).
 
 ### `calc_IEU()`
 

R/calc_Huntley2006.R

@@ -866,9 +866,14 @@ calc_Huntley2006 <- function(
             col = adjustcolor("grey", alpha.f = 0.5), border = NA)
 
     ## add simulated curve -------
+    xNew <- seq(if (mode_is_extrapolation) par()$usr[1] else 0,
+                par()$usr[2], length.out = 200)
+    yNew <- predict(GC.simulated@data$Fit, list(x = xNew))
+    if (normalise)
+      yNew <- yNew / A
     points(
-      x = natdosetimeGray,
-      y = LxTx_simulated$LxTx,
+      x = xNew,
+      y = yNew,
       type = "l",
       lty = 3)