[R] Population abundance, change point

vito.muggeo vito.muggeo at unipa.it
Wed Nov 17 10:38:21 CET 2010

dear Nick,
I do not know your data, however it seems to me that the pattern of relative abundance
of salamanders should not exhibit a sudden change, but rather a gradual change.

If this is the case, have a look to the segmented package and references therin. In
particular have a look to the relevant Rnews paper 

Segmented: an R package to fit regression models with broken-line relationships. R News,
8, 1: 20-25

at http://cran.r-project.org/doc/Rnews/Rnews_2008-1.pdf

Hope this helps you,

On Tue, 16 Nov 2010 17:30:49 -0500, Nicholas M. Caruso wrote
> I am trying to understand my population abundance data and am looking into
> analyses of change point to try and determine, at approximately what point
> do populations begin to change (either decline or increasing).
> Can anyone offer suggestions on ways to go about this?
> I have looked into bcp and strucchange packages but am not completely
> convinced that these are appropriate for my data.
> Here is an example of what type of data I have
> Year of survey (continuous variable) 1960 - 2009 (there are gaps in the
> surveys (e.g., there were no surveys from 2002-2004)
> Relative abundance of salamanders during the survey periods
> Thanks for your help, Nick
> -- 
> Nicholas M Caruso
> Graduate Student
> CLFS-Biology
> 4219 Biology-Psychology Building
> University of Maryland, College Park, MD 20742-5815
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