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

baptiste auguie baptiste.auguie at googlemail.com
Tue May 18 15:02:26 CEST 2010

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)]))
# 8
#  2.462951e-15

Suggestions / comments are welcome.

Best regards,


R version 2.11.0 RC (2010-04-16 r51754)

[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

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