Hi all:I am trying to fit a SOM which is usually carried out in two steps. At each step, different parameters (learning rate, neighbourhood and number of epochs) need to be used.The SOM package is based on SOM-PAK (http://www.cis.hut.fi/research/papers/som_tr96.ps.Z). In the HTML help different strategies seem to be correct though I cannot find out how to fine tune the parameters asociated to each of the two steps:1. In the HELP example the following appearsdata(yeast)
yeast <- yeast[, -c(1, 11)]
yeast.f <- filtering(yeast)
yeast.f.n <- normalize(yeast.f)
foo <- som(yeast.f.n, xdim=5, ydim=6)
foo <- som(yeast.f.n, xdim=5, ydim=6, topol="hexa", neigh="gaussian")
plot(foo)
As you may notice there are two different lines with foo<-som(...)My question is as follows: Does this mean that the first line and associated attributes starting withfoo<-som(..) corresponds exclusively to the 1st phase and the second line foo<-som(..) corresponds to the second phase and associated attributes of the same SOM being fitted?2. There are two additional functions which seem to carry out the same task, namely 'som.init' and 'som.update' The second question is: Would we reach the same final SOM if the first lineinstead of foo<-som(..)were foo<-som.init(...)and the second foo<-som(...) were foo<-som.update(...) ? Could we fine tune the parameters for the fitting process in this way(first phase with som.init and second phase with som.update)?Thank youGabriel Ibarra-BerastegiUniversity of the Basque CountrySPAIN


      
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