Neural network with negative output ?

hi, i have problem with Neural network using nntool, i have a some negative data in the output! there is relation between this in the input range ? and how can i define the input range ? i use the logsig and pureline transfer function,

thanks in advance,

[Greg Heath]

Need more details.

Have you looked at plots of the input, target, and target vs input?

Greg

[reda yagoub]

but why ! i need a output with only positive values, how can i choose the input range! thanks

[Greg Heath]

Your comment doesn't make any sense.

You should ALWAYS plot your input, output and output vs input

The range of input and target are properties of the given data. Not sure what you mean by choosing them.

Always choose tansig in the hidden layer

In general, the output layer is linear

HOWEVER for specific cases:

Use tansig if the output is bounded in [ -1,1]

Use logsig if the output is bounded in [ 0,1]

Hope this helps.

Greg