[R] Neural Network

Francis_Statistics statistics_vi at hotmail.com
Fri Mar 5 10:13:09 CET 2010


Hi,


We are trying to implement a early stopping rule with validation set on a
neural network. We’re using the AMORE package
(http://rwiki.sciviews.org/doku.php?id=packages:cran:amore) of R and when
you train the network you have to specify following variables:
Pval
Tval

What do we have to put here, or how do we have to specify this values? We
are using simulated data from a sinc function. 

This is the code that we are using. 

#define a sinc function 
sinc <- function(x) sin(pi*x)/(pi*x)
size_data = 200

# Generate data from sin function
ticks = linspace(-1,1,size_data)
sin_data = sinc(ticks)

# Generate noise
std_dev = 0.5
noise_data <- runif(size_data, 0, std_dev)

# Impose noise on sin data
dat = sin_data + noise_data

#Normalise data
max_dat = max(dat)
norm_dat = dat/max(dat)

#Define a neural network
net.start <- newff(n.neurons=c(1,20, 1),      
             learning.rate.global=1e-3,        
             momentum.global=0.5,
             error.criterium="LMS",           
             Stao=NA, hidden.layer="tansig",   
             output.layer="purelin",         
             method="ADAPTgd")

#Train the network
result <- train(net.start, ticks, norm_dat, Pval= NULL, Tval=NULL,
error.criterium="LMS", report=FALSE, show.step=8000, n.shows=0)


Are there any tips you can give for a better neural network or a better
training of this net? 

Thanks a lot,

A desperate team in search of help. 

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