R help - May 2010 - lattice::panel.levelplot.raster too picky with unequal spacing

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")

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 Augui?

Departamento de Qu?mica F?sica,
Universidade de Vigo,
Campus Universitario, 36310, Vigo, Spain

tel: +34 9868 18617
http://webs.uvigo.es/coloides

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 Augui?
>
> Departamento de Qu?mica F?sica,
> Universidade de Vigo,
> Campus Universitario, 36310, Vigo, Spain
>
> tel: +34 9868 18617
> http://webs.uvigo.es/coloides
> ____________________
>
>