ECOLOGICAL NICHE FACTOR ANALYSIS

The ENFA summarises the many, redundant EGVs into uncorrelated niche factors. Studying these factors and other results will give you a better ecological understanding of the focal species.



Operations

You are now ready to perform the Ecological Niche Factor Analysis. This will give you many outputs (scores matrix, etc.) that you should examine attentively in order to verify them and to get ecological understanding about the focal species. Now, you have got your Ecological Niche model.
  1. Compute the covariance matrix (Multivariate analyses/Matrix/Covariance matrix)
  2. Save the project to include the covariance matrix (thus you will not have to compute it again the next time) (Files/Save Project As...)
  3. Do an Ecological Niche Factor Analysis (ENFA) (Multivariate analyses /Factors/ENFA). The scores of this analysis (=the eigenvectors) will be saved automatically and can be got again later by the mean of the menu Multivariate analyses /Factors/Open. Note that invoking this menu will automatically launch the covariance matrix computation if it was not yet done; you can therefore jump over the two first steps of this process.
  4. Check the eigenvalues (they must all be greater than or equal to zero)
  5. Study carefully the results of the analysis. See the FAQ for further information about these results.


Links


References

  • Hirzel A.H., Hausser J., Chessel D. & Perrin N. (2002) Ecological-niche factor analysis: How to compute habitat- suitability maps without absence data? Ecology, 83, 2027-2036.