R devel - Mar 2008 - data(lh) time serie parameters

Dear all,

I'm confused by the time serie parameters in data(lh) :

sueoka:~ lobry$ R --vanilla --quiet
>  tsp(lh)
[1]  1 48  1

because documentation says:

QUOTE
A regular time series giving the luteinizing hormone in blood
samples at 10 mins intervals from a human female, 48 samples.
UNQUOTE

So that I would expect the time serie to end at 480 minutes
or 8 hours. Shouldn't we have something like:
>  tsp(lh) <- c(10, 480, 0.1) # in Minutes
or
>  tsp(lh) <- c(1/6, 8, 6)    # in Hours
Best,

Jean
>  sessionInfo()
R version 2.6.2 (2008-02-08)
i386-apple-darwin8.10.1

locale:
C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] rcompgen_0.1-17

-- 
Jean R. Lobry            (lobry at biomserv.univ-lyon1.fr)
Laboratoire BBE-CNRS-UMR-5558, Univ. C. Bernard - LYON I,
43 Bd 11/11/1918, F-69622 VILLEURBANNE CEDEX, FRANCE
allo  : +33 472 43 27 56     fax    : +33 472 43 13 88
http://pbil.univ-lyon1.fr/members/lobry/

On Sun, Mar 30, 2008 at 5:52 AM, Jean lobry
<lobry at biomserv.univ-lyon1.fr> wrote:
> Dear all,
>
> I'm confused by the time serie parameters in data(lh) :
>
> sueoka:~ lobry$ R --vanilla --quiet
> >  tsp(lh)
> [1]  1 48  1
>
> because documentation says:
>
> QUOTE
> A regular time series giving the luteinizing hormone in blood
> samples at 10 mins intervals from a human female, 48 samples.
> UNQUOTE
>
> So that I would expect the time serie to end at 480 minutes
> or 8 hours. Shouldn't we have something like:
>
> >  tsp(lh) <- c(10, 480, 0.1) # in Minutes
>
> or
>
> >  tsp(lh) <- c(1/6, 8, 6)    # in Hours
It seems they are using 10 minutes as the unit of measurement.
If you wish to change it to hours you might want to use this instead:

   lh.hr <- ts(lh, start = 0, frequency = 6)

so that

   cycle(lh.hr)

starts out at 1.

>
>It seems they are using 10 minutes as the unit of measurement.
>If you wish to change it to hours you might want to use this instead:
>
>    lh.hr <- ts(lh, start = 0, frequency = 6)
>
>so that
>
>    cycle(lh.hr)
>
>starts out at 1.
Dear Gabor,

yes, it is very likely that the original dataset was with a 10 minutes
unit of measurement because plot(lh[1:44]) yields the same curve as
figure 1b in:

@article{DigglePJ1991,
     title = {Nonparametric comparison of cumulative periodograms},
     author = {Diggle, P.J. and Fisher, N.I.},
     journal = {Applied Statistics},
     volume = {40},
     pages = {423-434},
     year = {1991}
}

whose legend reads:

QUOTE
Fig. 1. Four time series of LH concentrations in blood samples: each
series consists of $n = 44$ values derived from blood samples taken at
10-min intervals from a healthy adult female (data collected by Dr A.
Murdoch): a) early follicular phase, first cycle; (b) early follicular
phase, second cycle; (c) late follicular phase, first cycle; (d) late
follicular phase, second cycle
UNQUOTE

The complete multiple time series with 48 values as in data(lh) was
deposited in statlib by P.J. Diggle himself:
http://lib.stat.cmu.edu/datasets/diggle
(note that the first one has 4 trailling 0 that look like NA which
may explain why there were only 44 values in the 1991 paper).

What I found confusing is that

plot(lh)

ends at 48 when the doc says that lh is a "regular time series".
That would be OK for me if lh was a simple vector, but lh is a
time series so I would expect it to have different tsp() parameters
to fit the doc.

Best,

Jean
-- 
Jean R. Lobry            (lobry at biomserv.univ-lyon1.fr)
Laboratoire BBE-CNRS-UMR-5558, Univ. C. Bernard - LYON I,
43 Bd 11/11/1918, F-69622 VILLEURBANNE CEDEX, FRANCE
allo  : +33 472 43 27 56     fax    : +33 472 43 13 88
http://pbil.univ-lyon1.fr/members/lobry/