R Under development (unstable) (2025-09-08 r88798 ucrt) -- "Unsuffered Consequences"
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> ## Tests for non-standard evaluation in layer()
> 
> library(lattice)
> library(latticeExtra)
> oopt <- lattice.options(panel.error = NULL)
> 
> xx <- 1970
> xyplot(nhtemp) + layer(panel.abline(v = xx))
> 
> layer.test1 <- function() {
+     xyplot(nhtemp) + layer(panel.abline(v = xx))
+ }
> layer.test1()
> 
> layer.test2 <- function() {
+     vline <- 1920
+     xyplot(nhtemp) + layer(panel.abline(v = vline))
+ }
> try(plot(layer.test2()), silent = TRUE) # fails
> 
> layer.test3 <- function() {
+     zz <- 1930
+     ls.str(environment())
+     xyplot(nhtemp) + layer(panel.abline(v = vline),
+                            data = list(vline = zz))
+ }
> layer.test3()
> 
> layer.test4 <- function() {
+     zz <- 1940
+     xyplot(nhtemp) + layer(panel.abline(v = c(zz, xx)),
+                            data = environment())
+ }
> layer.test4()
> 
> do.call(lattice.options, oopt)
> 
> 
> 
> 
> proc.time()
   user  system elapsed 
   0.39    0.09    0.46