Bell Eapen MD, PhD.

Neural Network and deep-learning are the buzzwords lately. Machine learning has been in vogue for some time, but the easy availability of storage and processing power has made it popular. The interest is palpable in business schools as well. The ML related techniques have not percolated much from the IT departments to business, but everybody seems to be interested. So, let us build a Neural Network model in 10 minutes.

This is the scenario:

You have a collection of independent variables (IV) that predict a dependent variable (DV). You have a theoretical model and want to know if it is good enough. Remember, we are not testing the model. We are just checking how good the IVs are in predicting DV. If they are not good predictors to start with, why waste time conjuring a fancy model! Sounds familiar? Let’s get started.

Setup

Do you have some preliminary knowledge of python? If not spend another 10 minutes here learning python. Now you have to spend some time to set up your system once. Just follow these instructions.

Code

The first step is to import few modules. If you don’t know what these are, just copy paste and ignore. Consider them as a header that you require.

# Modules
import sys
import numpy
from imblearn.over_sampling import RandomOverSampler
from keras.layers import Dense
from keras.models import Sequential
from pandas import read_csv

Create a CSV file with your data with the last column as your DV. Now import that file.

# Import data
dataset = read_csv(sys.argv[1], header=1)
(nrows, ncols) = dataset.shape

nrows and ncols are the numbers of rows and columns. Now separate DV (y) from IVs (X) as below.

# Separate DV from IVs 
values = dataset.values
X = values[:, 0:ncols-1]
y = values[:, ncols-1]

In most cases, you will be trying to predict a rare event. So add some oversampling for taste 🙂

# Oversampling
ros = RandomOverSampler(random_state=0)
X_R, y_R = ros.fit_sample(X, y)

Create, compile and fit the model.

# create model
model = Sequential()
model.add(Dense(12, input_dim=vnum, kernel_initializer='uniform', activation='relu'))
model.add(Dense(8, kernel_initializer='uniform', activation='relu'))
model.add(Dense(1, kernel_initializer='uniform', activation='sigmoid'))
# Compile model
model.compile(loss='binary_crossentropy', optimizer='adam', metrics=['accuracy'])
# Fit the model
model.fit(X_R, y_R, epochs=150, batch_size=10, verbose=2)

The three model.add statements represent the three layers in Neural Network. The number after Dense is the number of neurons in each layer. You can play with these values a bit. These settings should work in most business cases. Read this for more information.

Now evaluate the model.

# evaluate the model
scores = model.evaluate(X_R, y_R)
print("\n")
print("\n Accuracy of the model")
print("\n%s: %.2f%%" % (model.metrics_names[1], scores[1] * 100))
print("\n --------------------------------------------------")

Put this code in a file (say nnet.py) and use it as below.

python nnet.py mydata.csv

TL;DR

Just use QRMine. nnet.py is in there.

Operationalizing Neural Network models

Shortly, I will show you how to operationalize a model using flask.