[R] Problem with Trellis graphics in nlme
Thomas W Blackwell
tblackw at umich.edu
Thu Nov 20 23:02:33 CET 2003
It seems just possible that the difficulty may have nothing to do
with nlme() or any other data analysis. The graph you describe
could result if one of the y-values was five time as large as any
of the others. This could result from an error in reading the
data input file, a missing decimal point somewhere, etc.
In order to diagnose this, do range(data$y) (assuming that you
are plotting a data frame named "data" with a column named "y"),
data[ data$y == max(data$y), ]
to look at just the offending row(s).
Another possibility is that somehow you are setting "ylim" in the
plotting command, but I assume you've excluded that one already.
HTH - tom blackwell - u michigan medical school - ann arbor -
On Thu, 20 Nov 2003, anthony staines wrote:
> I would be grateful for help with a problem which is irritating me.
> I am quite sure that I am doing something stupid, but I can't see what it
> I am running R 1.7 on Windows 2000. The graphics device is the PC screen.
> The graphics from the nlme demonstration in Bates an Pinheiro's manual work
> just as advertised. The CO2 data and the Orthodont data dsiplay
> beautifully.(plot(Orthodont, outer=true, key=false) However. when I try to
> analyse a data set of my own, of about 2,770 measurements on 293 women the
> graphics go very peculiar. The graphics in the example from the manual fill
> most of the vertical extent of the graphics device. My graphics are correct
> horizontally, but are confined to about one-fifth of the vertical extent of
> the graphics device. As a result they look odd, and are almost usless for
> analysis. They do seem, however, to be the correct graphics (In this case
> maternal weight against gestational age for two groups of women).
> I have read the manual for the lattice commands, and the nlme command, and
> indeed for the plain plot command, but failed to get any ideas. Roughly, I
> need to tell lattice to use the full vertical extent of the display device.
> If it helps, I can e-mail the offending images to you individually on
> Anthony Staines,
> Public Health,
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