[R] strange spectrum() plot

Petr Pikal petr.pikal at precheza.cz
Mon Jan 22 15:19:37 CET 2001

Dear R-users
I am a beginner and I use some functions without deep understanding of 
math behind them - sorry :-(

I used a spectrum() function from ts library several times. I learned 
from sunspots dataset, that the result shall be a plot with peak(s). I can 
get also a list object with $freq, $spec values and of course some other.

I can make reciprocal of these $freq values which correspond to 
peak(s) at $spec value(s). In case of sunspots series I get something 
close to 11 and as I know that sun spots occurs at 11 year period I can 
deduct that the peak(s) indicates a periodic nature of time series and I 
can compute the time between periods.

My problem is that with my newest time series I have got a bit 
different plot not with peaks but with "valleys". (See attached picture)

My questions are:

Does anybody know if these valeys mean something? Can I deduct 
some facts about my time series from such plot?

The other question:

Can I mimic a peaks() function fro S+ in R?

I am using P133, 32mb memory, W95 and R 1.2.0 but I suppose it is 
irrelevant to my questions.

Thank you.

Petr Pikal
Precheza a.s.
Nabr.Dr.E.Benese 24
tel: 00420 641 25 2257
     +420 (0)724 008 364
     petr.pikal at precheza.cz
     p.pik at volny.cz

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