[R] Help with short time series
simone.vincenzi at nemo.unipr.it
Mon Aug 7 22:07:21 CEST 2006
Thanks for the help.
I provide below the dataset I'm using, it's a little bit different from what
I was describing (sorry for that). The streams are 3 and I have an unequal
number of years for each stream.
Stream Density Year
1 Zak 0.20 2000
2 Zak 0.36 2001
3 Zak 0.41 2002
4 Zak 0.34 2003
5 Zak 0.28 2004
6 Gor 0.08 1999
7 Gor 0.05 2000
8 Gor 0.14 2001
9 Gor 0.16 2002
10 Gor 0.13 2003
11 Gat 0.18 2004
12 Gat 0.10 2001
13 Gat 0.37 2002
14 Gat 0.57 2003
15 Gat 0.47 2004
I tried to follow the suggestions of Dieter, but the model does not fit.
Any suggestion will be appreciated
> I have a statistical problem with the comparison of two short time-series
> density data in an ecological framework. I have to compare two short time
> series (5 years, one value for each year) of species density data (it is
> density of fish in two different streams) to test if the two means of the
> five densities are significantly different, so basically if the two mean
> stream-specific fish densities are significantly different.
> I don't think I can use a straight t-test due to the problem of
> autocorrelation and I don't think I can use a repeated measure ANOVA as I
> don't have any replicates.
> Any help would be greatly appreciated.
try something like
This should also give you an estimate if the slopes are different if you
against the simplified model
Since you did not provide a short example data set, this is only
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