Classifying hand written digits dataset using Probabilistic neural network (PNN)? I am trying to apply Probabilistic Neural Network (PNN) on MNIST dataset using MATLAB on 28000 samples. I tried to build the model but it gave an error saying matrix dimension exceeds memory showing it will require 5.08 GB (28000x28000) matrix.
I want to know should I decrease the number of samples as input for training from 28000 to 200 samples as I read in research paper.
Should I reduce the sample size or is there something else wrong?
is pnn only applicable on small data sets?
Reducing the sample size is pretty much up to you.  PNN have the drawback that the size of the network after training is equal to the size of the training dataset.  Therefore it's a bit impractical to use for large datasets.  I also believe that there is evidence that suggest the performance may also decrease when the layers are big.

I don't have access to the paper but I imagine a big reason why they reduced the sample was to avoid the memory error that you're encountering right now.  I also suspect they carefully selected a good representation for the sample.