[R-sig-eco] Randomization to obtain p-values

[basille.web at ase-research.org]

Hey Barnabas,

You could check the ade4 package for this, and the function:

?as.randtest

Look at the example there, and the details of the computation of the 
p-values (which is very straightforward).

Mathieu.


Le 08/23/2013 03:07 AM, BARNABAS DARU a écrit :
> Dear R members –
> I write to seek help concerning simulation and randomization.
> I have a set equal area grids with observations e.g. phylogenetic observation, per grid.
> I would like to be able to simulate random observations e.g. 1000 times to obtain a null distribution of the observation. I will then be glad to know how to test the observed patterns against the null to obtain p-values.
> The data is arranged as follows:
>
> grids1  observatn
> g0      71.193510
> g1      110.338347
> g2      155.553859
> g3      178.696210
> g4      139.272733
> g5      120.913020
> g6      112.945412
> g7      106.012243
> g8      80.889829
> g9      95.196947
> g10     182.268465
> g11     195.393473
> g12     198.778229
> g13     177.343460
> g14     167.527703
> g15     167.046954
> g16     169.810604
> g17     166.792720
> g18     139.586739
> g19     138.117178
> g20     129.415400
> …
> I simply want to be able to show a histogram of the null distribution and a point showing how significant the observed is from the null as well as the confidence intervals.
> Any R code will be greatly appreciated.
>
> Thanks and kind regards
> Barnabas Daru
>
>
>
>
>
>
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>   /---/ Barnabas Daru
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> #…if you can think it, you can do it.
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Mathieu Basille, PhD

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University of Florida \\
Fort Lauderdale Research and Education Center
(+1) 954-577-6314
http://ase-research.org/basille

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