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

> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: oc2plot
> ### Title: Plot First Differences from Ordinal DV Model
> ### Aliases: oc2plot
> 
> ### ** Examples
> 
> library(MASS)
> data(france)
> polr.mod <- polr(vote ~ age + male + retnat + lrself, data=france)
> typical.france <- data.frame(
+ 	age = 35, 
+ 	retnat = factor(1, levels=1:3, labels=levels(france$retnat))
+ 	)
> oc.res <- ordChange(polr.mod, data=france, typical.dat=typical.france, sim=TRUE)	

Re-fitting to get Hessian

> oc2plot(oc.res)
Warning in order(as.numeric(x)) : NAs introduced by coercion
Warning in diff(as.numeric(x[ord])) : NAs introduced by coercion
Warning in prepanel(lower = c(-0.0605505372293052, -0.0422187084919278,  :
  NAs introduced by coercion
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in order(as.numeric(x)) : NAs introduced by coercion
Warning in diff(as.numeric(x[ord])) : NAs introduced by coercion
Warning in prepanel(lower = c(-0.0605505372293052, -0.0422187084919278,  :
  NAs introduced by coercion
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in order(as.numeric(x)) : NAs introduced by coercion
Warning in diff(as.numeric(x[ord])) : NAs introduced by coercion
Warning in prepanel(lower = c(-0.0605505372293052, -0.0422187084919278,  :
  NAs introduced by coercion
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in order(as.numeric(x)) : NAs introduced by coercion
Warning in diff(as.numeric(x[ord])) : NAs introduced by coercion
Warning in prepanel(lower = c(-0.0605505372293052, -0.0422187084919278,  :
  NAs introduced by coercion
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Warning in min(x) : no non-missing arguments to min; returning Inf
Warning in max(x) : no non-missing arguments to max; returning -Inf
Error in valid.viewport(x, y, width, height, just, gp, clip, xscale, yscale,  : 
  invalid 'xscale' in viewport
Calls: <Anonymous> ... printFunction -> pushViewport -> viewport -> valid.viewport
Execution halted