help in neural network

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muhammed kareem
muhammed kareem on 28 Oct 2014
Answered: Greg Heath on 7 Nov 2014
Hello every one I am try to make neural network to predict permeability in oil field from wireline log so I have 5 input and one target I normaliz data to -1 and 1 but when I train network did not give me good r2 just 0.58 some time 0.62 what I do to reach r2 0.92 Many thanks muhammed
  2 Comments
Greg Heath
Greg Heath on 28 Oct 2014
Insufficient info.
size(input) [5 N ]
size(output) [ 1 N ]
Type of net fitnet ??
range of hidden Hmin:dH:Hmax ??
number of random weight trials for each value of H Ntrials ??
Any other non-default parameters??
muhammed kareem
muhammed kareem on 6 Nov 2014
thanks dear Greg my input is 5*251 my target is 1*251......... i use newff ...... i do not know how range my hidden and weight>>>>>>>>>>>>>>
this is my code
net = newff(p, t, 20, {'logsig', 'purelin'});
net.divideParam.trainRatio = 75/100;
net.divideParam.testRatio = 15/100;
net.divideParam.valRatio = 10/100;
net.trainParam.epochs = 400;
net.trainParam.goal = 0.000001;
net.trainParam.max_fail = 200;
net.trainParam.lr = 0.06;
[net tr] = train(net,p,t);
a=sim(net,test);
postreg(a,tt);

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Accepted Answer

Greg Heath
Greg Heath on 7 Nov 2014
The optimal value for H is usually obtained by trial and error. For each candidate value for H design Ntrials nets with different random initial weights.
I have posted many, many examples using a double for loop over H and weight initializations. Search NEWSGROUP and ANSWERS for the latest examples using
greg fitnet Ntrials
If you have the current functions FITNET (regression/curve-fitting)and PATTERNNET(classification/pattern-recognition) that automatically call FEEDFORWARDNET, use them instead of the OBSOLETE functions NEWFIT and NEWPR that automatically call NEWFF.
Hope this helps.
Thank you for formally accepting my answer
Greg

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