Running examples in ‘zenplots-Ex.R’ failed
The error most likely occurred in:

> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: extract_2d
> ### Title: Extracting information for our default/provided plot2d()
> ### Aliases: extract_2d
> 
> ### ** Examples
> 
> ## This function is used within the default (any user defined)
> ## 2d plot functions
> ##
> my_2d_plot <- function(zargs, your_name = "BillyBob", ...) {
+                    data_2d <- extract_2d(zargs)
+                    msg <- paste("Components of zargs available",
+                                 "to construct a 2d plot for ",
+                                 your_name)
+                    print(msg)
+                    ## just print the names of the data components
+                    ## which you might want to use in your plot
+                    print(names(data_2d))
+ 
+                    ## You can plot whatever you want using the information in
+                    ## could use any of these to construct any 1d plot you want
+                    ## using R's graphics or any of zemplot's built in 1d plots.
+                    ##
+                    ## For example, here we could use
+                    ## use zenplot's base graphics functions
+                    ## First a scatterplot
+                    points_2d_graphics(zargs, ...)
+                    ## to which we overlay density contours
+                    density_2d_graphics(zargs, add = TRUE, col = "steelblue", ...)
+                    ## similar functions could be called for the other packages.
+                    ## You can print the source of anyone of the default functions
+                    ## to get some idea of managing details.
+                 }
> 
> ## And now try it out
> zenplot(iris, plot2d = my_2d_plot)
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
[1] "Components of zargs available to construct a 2d plot for  BillyBob"
 [1] "x"          "y"          "xcols"      "groups"     "vars"      
 [6] "glabs"      "vlabs"      "xlim"       "ylim"       "same.group"
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
[1] "Components of zargs available to construct a 2d plot for  BillyBob"
 [1] "x"          "y"          "xcols"      "groups"     "vars"      
 [6] "glabs"      "vlabs"      "xlim"       "ylim"       "same.group"
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
[1] "Components of zargs available to construct a 2d plot for  BillyBob"
 [1] "x"          "y"          "xcols"      "groups"     "vars"      
 [6] "glabs"      "vlabs"      "xlim"       "ylim"       "same.group"
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
[1] "Components of zargs available to construct a 2d plot for  BillyBob"
 [1] "x"          "y"          "xcols"      "groups"     "vars"      
 [6] "glabs"      "vlabs"      "xlim"       "ylim"       "same.group"
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Warning in FUN(X[[i]], ...) : NAs introduced by coercion
Error in if (any(h <= 0)) stop("bandwidths must be strictly positive") : 
  missing value where TRUE/FALSE needed
Calls: zenplot ... do.call -> <Anonymous> -> density_2d_graphics -> kde2d
Execution halted