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ade4 and inertia of axis 2

2 messages · John Poulsen, Stéphane Dray

#
Hello,

Could someone please tell me how to find the estimate of inertia for the 
second axis of an RLQ analysis using ade4? Using the example from the 
ade4 package, I *suspect* that the inertia for the 2nd axis of the R 
table would be 4.139332 (see below results summary from rlq1).  However, 
the row is labeled "12" not "2" which suggests this is not correct.  In 
addition, this would mean that axis 2 of the RLQ would explain more than 
100% of the inertia of the separate ordination for dudimil 
((100*4.139)/dudimil$eig[2]=176%) which I believe is not supposed to occur.

Could anyone set me straight by either letting me know how to get the 
inertia for axis 2 or that my thinking is perhaps wrong?

Thanks,
John

data(aviurba)
  coa1 <- dudi.coa(aviurba$fau, scannf = FALSE, nf = 2)
  dudimil <- dudi.hillsmith(aviurba$mil, scannf = FALSE, nf = 2, row.w = coa1$lw)
  duditrait <- dudi.hillsmith(aviurba$traits, scannf = FALSE, nf = 2, row.w = coa1$cw)
  rlq1 <- rlq(dudimil, coa1, duditrait, scannf = FALSE, nf = 2)
  plot(rlq1)
  summary(rlq1)
  randtest.rlq(rlq1)
Eigenvalues decomposition:
       eig     covar      sdR      sdQ      corr
1 0.4782826 0.6915798 1.558312 1.158357 0.3831293
2 0.1418508 0.3766308 1.308050 1.219367 0.2361331

Inertia & coinertia R:
   inertia      max     ratio
1  2.428337 2.996911 0.8102800
12 4.139332 5.345110 0.7744148

Inertia & coinertia Q:
   inertia      max     ratio
1  1.341791 2.603139 0.5154512
12 2.828648 4.202981 0.6730098

Correlation L:
      corr       max     ratio
1 0.3831293 0.6435487 0.5953384
2 0.2361331 0.5220054 0.4523576
#
Dear John,

In RLQ (similarly to other methods in ade4), inertia are given by 
eigenvalues. Thus, the percentage of inertia are obtained simply by:

rlq1$eig/sum(rlq1$eig)*100

For more details on outputs or RLQ, you can have a look at 
http://listes.univ-lyon1.fr/wws/arc/adelist/2009-03/msg00001.html

Lastly, if you have questions about ade4, please subscribe and send an 
email to adelist (http://listes.univ-lyon1.fr/wws/info/adelist)

Cheers.
John Poulsen wrote: