aula 26 goodies - ulisboa · ordered along the canonical axes following their ecological optima....
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Aula 26 Goodies*
* Goodies related to animals, plants and numbers…
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What is this?
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Já falta pouco…!
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https://www.davidzeleny.net/anadat-r/doku.php/en:start
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https://www.azquotes.com/quote/819974
Ecologia Numérica - Aula Teórica 26 – 16-12-2018
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Constrained Ordination
Regressão multiplaY~X
Espécies (Y) por locais
Variáveisambientais
(X) por locais
PCARedundancy
Analysis
CACanonical
Correspondence Analysis
Unconstrained Ordination
Espécies por locais
Variáveis ambientais por locais
Caracteristicas por objectos
PCA (preserva distanciaseuclideanas)
CA (preserva distânciasdo qui-quadrado)
Componentes sãocombinações linearesdas variáveis originais
Sobre ospreditores
lineares
Not in our program
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ordenação
• Modificação da CA, na qual os eixos são extraídos não só
tendo em conta a maximização da inércia (variância)
explicada, mas também de modo a que a sua correlação com
outro conjunto de variáveis (usualmente variáveis
ambientais) seja também maximizada;
• A CCA utiliza também o algoritmo de reciprocal averaging.
Análise canónica de correspondências (CCA)
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ordenação
• Ambas as análises, CA e CCA, maximizam a dispersão dos
pontos ao longo dos eixos;
• A principal diferença reside no facto que numa CA esta
dispersão é independente de outra matriz com variáveis
ambientais, enquanto que na CCA os eixos são uma função
desta matriz.
Análise canónica de correspondências (CCA)
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CCA shares the basic properties of CA, combined with those of aconstrained ordination.
It preserves the χ2 distance among sites, and species arerepresented as points in the triplots.
ter Braak (1986) has shown that, provided that some conditions are fulfilled, CCA is a good approximation of a multivariateGaussian regression.
One particularly attractive feature of a CCA triplot is that species are ordered along the canonical axes following their ecological optima.
This allows a relatively easy ecological interpretation of species assemblages. Also, species scores can be used as synthetic descriptors in a clustering procedure (for instance k-means partitioning) to produce a typology of the species in assemblages.
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ordenação
1ºeixo
2ºeixo
-1.0 1.0
-1.0
1.0
Gobius n
MonochirEngrauli Diplodus
Halobatr
Pomatosc
ArnoglosSolea so
Sarpa sa
Symphodu
Atherina
Calliony
Solea se
Diplodus
Hippocam
temp
sal
od
prof
transp
1
2
3
4
5
6
7
8
9 10
11
12
13
14
15
16
17
18
19
20
Análise canónica de correspondências (CCA)
Diagrama deOrdenação
(CCA)
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ordenação
Análise canónica de correspondências (CCA)
Da variação total nas abundancias, quanta é explicada por cadacomponente, primeiro em funçãodas variáveis ambientais, e depoisnos eixos não-constrained
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Da variação nasabundancias que podeser explicada pelasvariáveis ambientais, quanta é explicada por cada componente?
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ordenação
Análise canónica de correspondências (CCA)