[R] lattice::panel.levelplot.raster too picky with unequal spacing

[Deepayan Sarkar]

On Tue, May 18, 2010 at 6:32 PM, baptiste auguie
<baptiste.auguie at googlemail.com> wrote:
> Dear all,
>
> I got a couple of warnings using panel.levelplot.raster,
>
> In panel.levelplot.raster(..., interpolate = TRUE) :
>  'y' values are not equispaced; output will be wrong
>
> although I was quite sure my data were equally spaced (indeed, I
> created them with seq()). A closer look at the source code reveals
> that the function tests for exact uniformity in grid spacing,
>
>  if (length(unique(diff(uy))) != 1)
>            warning("'x' values are not equispaced; output will be wrong")

Maybe a better test would be

isTRUE(all.equal(diff(range(diff(ux))), 0))

I'll try that out for the next release.

-Deepayan

>
> The following dummy example would suggest that a strict equality is
> not always suitable,
>
> x <- seq(0, 50, length=100)
> ux <- sort(unique(x[!is.na(x)]))
> length(unique(diff(ux)))
> # 8
> sd(unique(diff(ux)))
> #  2.462951e-15
>
> Suggestions / comments are welcome.
>
> Best regards,
>
> baptiste
>
>
> sessionInfo()
> R version 2.11.0 RC (2010-04-16 r51754)
> i386-apple-darwin9.8.0
>
> locale:
> [1] en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] lattice_0.18-5
>
> loaded via a namespace (and not attached):
> [1] grid_2.11.0  tools_2.11.0
>
>
>
> --
> ____________________
>
> Baptiste Auguié
>
> Departamento de Química Física,
> Universidade de Vigo,
> Campus Universitario, 36310, Vigo, Spain
>
> tel: +34 9868 18617
> http://webs.uvigo.es/coloides
> ____________________
>
>