en:forward_sel_r
Section: Ordination analysis
Variable selection (constrained ordination)
R functions
ordistep
(libraryvegan
) - variable selection function, which is applicable with functionsrda
,cca
orcmdscale
. Offers forward, backward and combined step-wise selection algorithm (specified by argumentdirection
). Comparison of variables is based on AIC criteria and P-values from Monte Carlo permutation test.ordiR2step
(libraryvegan
) - similar toordistep
, but based on R2adj, and implements three stopping stopping rules when selecting the variables: if R2adj of the selected model starts to decrease, or R2adj of global model (defined inscope
) is exceeded, or any remaining variable is not significant at predefined P-value. It can be used withrda
,cca
orcapscale
. (Before, this function used to be limited to onlyrda
andcapscale
, but recently vegan implements the permutation method of estimating adjusted R2 for CCA (Peres-Neto et al. 2006) into the function RsquareAdj, and since then theordir2step
function can handle also formula withcca
function.)forward.sel
(libraryadespatial
) - variable selection method, which is implicitly using RDA ordination, and offers only forward selection (not backward or step-wise). Contains stopping rules from Borcard et al. 2008, the same asordiR2step
, but has different logic of setting the arguments. Eventually, however, it returns the same results asordiR2step
and could be favoured for rather easy use (no need to specify null and full models and the scope).
en/forward_sel_r.txt · Last modified: 2022/03/30 10:34 by David Zelený