# [R] Is there a function for finding local extrema.

Philippe Grosjean phgrosje at ulb.ac.be
Fri Jul 26 17:23:23 CEST 2002

```To find extrema, you have the turnpoints() function in the optional package
pastecs. Once pastecs is installed on your system, use:

library(pastecs)
example(turnpoints)
?turnpoints

For your particular problem, you can use:
X <- runif(100000)
extract(turnpoints(X), 100000, peak=1, pit=0)

Depending on what you are looking for, you may be interested by additional
statistics about extrema, which is provided by turnogram().
Best regards,

Philippe Grosjean

...........]<(({°<...............<°}))><...............................
( ( ( ( (
) ) ) ) )      Philippe Grosjean
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( ( ( ( (       e-mail: phgrosjean at sciviews.org
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( ( ( ( (      "I'm 100% confident that p is between 0 and 1"
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.......................................................................

-----Message d'origine-----
De : owner-r-help at stat.math.ethz.ch
[mailto:owner-r-help at stat.math.ethz.ch]De la part de Witold Eryk Wolski
Envoyé : vendredi 26 juillet 2002 15:46
À : r-help at stat.math.ethz.ch
Objet : [R] Is there a function for finding local extrema.

I have a vector with about 100.000 values representing a quite regular
function (sinusoid like).
I would like to find all local maxima of this function (should be about
4000). Is there a native routine for R?
Eryk.

--
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´v´  'v´ \'v'/ MPI Moleculare Genetik     fax  :0049-(0)30-8413-1139 | |
/| |\/| |\ | |  Mass Spectrometry Group    http://www.molgen.mpg.de  /.^.\
m m  m m  m m  mail :wolski at molen.mpg.de                             /|\

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