[R] plot spaghetti data

[Douglas Bates]

To elaborate a bit on Harold's reply, the use of a "spaghetti plot"
for more than 4 or 5 groups is not recommended.  Consider the
longitudinal data "sleepstudy" in the Matrix package.  A spaghetti
plot can be produced by

> data(sleepstudy, package = "Matrix")
> library(lattice)
> xyplot(Reaction ~ Days, sleepstudy, groups = Subject, type = c('g','l'), aspect = 'xy')

Now compare this to the result of

> xyplot(Reaction ~ Days | Subject, sleepstudy, type = c('g','p','r'), aspect = 'xy')

which is a lattice plot with the data for each subject in a separate
panel.  Even better is to use

> xyplot(Reaction ~ Days | Subject, sleepstudy, type = c('g','p','r'), aspect = 'xy',
+        index.cond = function(x, y) coef(lm(y ~ x))[1])

where the panels are ordered according to a characteristic of the data
(the intercept for the per-subject regression line) rather than in the
more-or-less random order created by the subject number.


library(lattice)
xyplot(Reaction ~ Days

On 9/16/05, Doran, Harold <HDoran at air.org> wrote:
> There is interaction.plot(), but, the trellis graphics in lattice are
> much better. You might want to check these out.
> 
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Marc Bernard
> Sent: Friday, September 16, 2005 8:58 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] plot spaghetti data
> 
> Dear All,
> 
> I  wonder if there is an R function to plot longitudinal data (spaghetti
> plots)...
> I've seen the function "is.longitudinal" but without any succes...
> 
> Thanks a lot in advance,
> 
> Bernard
> 
> 
> ---------------------------------
> 
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