how to do satellite image classification based on NDVI values using Matlab?

hi, I m working in matlab to classify a satellite image on d basis of NDVI values. I am using PNN. I have classified it but now I don't know how to use the object created to display the classified image. here is my code, plz if u can help

wheat = NaN * ones(2000000, 1); fodder = NaN * ones(2000000, 1); other = NaN * ones(2000000, 1);

img = imread('e:\ndvi\ndvi_2007009.tif');

w = img(img>0.5 | img==0.5); f=img(img<0.5 & img>=0.3 ); r=img(img<0.3);

wheat(1:length(w),1) = w;

fodder(1:length(f),1) = f;

other(1:length(r),1) = r;

P=[wheat,fodder,other];

T=[1,2,3];

net = newpnn(P,T); now I don't know how to use this object 'net' to display the classified colored image.