# Classification using neural net in r

October 9, 2013
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(This article was first published on Analytics , Education , Campus and beyond, and kindly contributed to R-bloggers)

This is mostly for my students and myself for future reference.

Classification is a supervised task , where we need preclassified data and then on new data , I can predict.
Generally we holdout a % from the data available for testing and we call them training and testing data respectively.  So it’s like this , if we know which emails are spam , then only using classification we can predict the emails as spam.

I used the dataset http://archive.ics.uci.edu/ml/datasets/seeds# .  The data set has 7 real valued attributes and 1 for predicting .  http://www.jeffheaton.com/2013/06/basic-classification-in-r-neural-networks-and-support-vector-machines/ has influenced many of the writing , probably I am making it more obvious.

The library to be used is library(nnet) , below are the list of commands for your reference

2.       Setting training set index ,  210 is the dataset size, 147 is 70 % of that
seedstrain<- sample(1:210,147)
3.       Setting test set index
seedstest <- setdiff(1:210,seedstrain)

4.       Normalize the value to be predicted , use that attribute of the dataset , that you want to predict
ideal <- class.ind(seeds\$Class)
5.       Train the model, -8 because you want to leave out the class attribute , the dataset had a total of 8 attributes with the last one as the predicted one
seedsANN = nnet(irisdata[seedstrain,-8], ideal[seedstrain,], size=10, softmax=TRUE)
6.       Predict on testset
predict(seedsANN, seeds[seedstrain,-8], type="class")
7.       Calculate Classification accuracy

table(predict(seedsANN, seeds[seedstest,-8], type="class"),seeds[seedstest,]\$Class)

Happy Coding !