error : "Argument to dynamic structure reference must evaluate to a valid field name" using Genetic Algorithms

Hi,

I am using a genetic algorithm to minimize the single output of a decision tree, which I succesfully trained previously, for just one of the inputs. And i get the error : "Argument to dynamic structure reference must evaluate to a valid field name". And I don't know what I am doing wrong.

Thanks for your help.

Find attached the code:

%Define Constants
ds=5;
v=100;
optDT = zeros(length(ds),length(v));
fvalDT = zeros(length(ds),length(v));

for q = 1:length(ds)
    for t = 1:length(v)

          FitnessfunDT = @(y) modelfunT(y,ds(q),v(t),net);

          [optDT(q,t),fvalDT(q,t)] = ga(FitnessfunDT,1,[],[],[],[],1,60,[],1);

      end
  end

%%%%%%

function berDT = modelfunT(y,ds,v,tree)
    berDT = tree.predict([y,ds,v]);
end

[Geoff Hayes]

Guillem - where has net been defined?