Hi Jesús,
If you are talking about gridded maps, you could consider Syrjala's test
(Stephen E. Syrjala 1996. A Statistical Test for a Difference between
the Spatial Distributions of Two Populations. Ecology 77:75–80.
http://dx.doi.org/10.2307/2265656). It is implemented in the ecespa package.
Cheers,
Marcelino
El 20/02/2014 19:51, Jesús Muñoz escribió:
Dear colleagues,
I needed to measure the association degree (and ideally its p-value) between
two maps, one representing richness of European bryophytes and the other
vascular plant richeness. From the maps it is clear the two patterns are
reversed: bryophytes 'rule' in the north, and vascular plant richness is
higher in southern Europe.
I have used isodata algorithm followed by a Maximum-likelihood
classification to generate a map showing four different areas in Europe
(lowbryo-lowvasc, lowbryo-highvasc, highbryo-lowvasc, and
highbryo-highvasc). Additionally, I would like to run a correlation analysis
but corrected for the univariate spatial correlation of each variable
(bryophytes and vascular plant richness); a global correlation map-to-map is
meaningless here.
I found a statistic that would suit my needs (Lee, S.-I. 2001. Developing a
bivariate spatial association measure: An integration of Pearson's r and
Moran's I. Journal of Geographical Systems 3(4): 369-385). It is implemented
in 'The Map Comparison Kit' (http://www.riks.nl/mck/), but it return values
outside the -1 to 1 values, which makes me think there is something wrong in
the code or the statistic.
Can somebody guide me to a R package allowing me to measure the association
between these two grids?
thanks in advance,
Jesús
*************************************************************************
Jesús Muñoz PhD e-mail: jmu...@rjb.csic.es
Real Jardín Botánico (CSIC)
C/ Claudio Moyano 1 tlf. +34 91 420 3017
E-28014 Madrid fax. +34 91 420 0157
ESPAÑA (Spain)
http://www.masterenbiodiversidad.org
http://www.rjb.csic.es/jardinbotanico/jardin/contenido.php?Pag=413&tipo=cien
tifico&cod=66
KRAKEN research group (environmental modelling, data processing & analysis):
http://www.unex.es/investigacion/grupos/kraken
SYNTHESYS: EU funds short visits to our institution:
http://www.synthesys.info/index.htm
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