[R-sig-eco] order of explanatory variables in vegan CCA

[Gregory, Matthew]

Hi all,

We run vegan CCA as part of an automated process.  Our typical use case is to read in species and environment matrices (from CSV files) and subset the environmental matrix with a vector of field names ('vars'), e.g. 

  spp <- read.csv(spp_file, row.names = id_field)
  env <- read.csv(env_file, row.names = id_field)
  env <- env[,vars]
  cca_obj <- cca(spp, env)

Today, for the first time, we received the following error:

  Error in La.svd(x, nu, nv) : error code 1 from Lapack routine 'dgesdd'

which from googling implies that the SVD did not converge.  If I reorder the 'vars' list and rerun, I can have it run to completion.  I am completely naïve with ordination modeling, but is there any reason why the order of environmental variables would matter to CCA?  I would have thought this wouldn't matter.

Thanks for any pointers.

matt