Neural Nets

What is an Artificial Neural Network?

An artificial neural network is a computational model that can be trained to recognize correlations between input data and a desired output

What can Neural Nets do?

Rooms

Age

Price

Predict House Price

Rooms: 5
Age: 10 years

Price: ?

Input Layer

Network Topology

Output Layer

Rooms

Age

100,000

-20,000

Price

100000(x_1) + -20000(x_2) = y
x_1
x_2
y
x_1
x_2
y
Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

4

10

?

Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

4

10

100000(4) + -20000(10) = 200000

200000

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

4

10

200000

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

4

5

?

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

4

5

300000

100000(4) + -20000(5) = 300000
Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

4

5

300000

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

4

0

?

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

Rooms

Age

100,000

-20,000

Price

4

0

400000

100000(4) + -20000(0) = 400000
Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000 $400,000 $188,000

Rooms

Age

100,000

-20,000

Price

4

0

400000

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000 $400,000 $188,000
-20000(x) + 400000 = y

Input Layer

Output Layer

Rooms

Age

Price

Hidden Layer(s)

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

w_1(x_1) + w_2(x_2) = y

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

f(w_1(x_1) + w_2(x_2)) = y

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

ReLU(w_1(x_1) + w_2(x_2)) = y
ReLU(x) = max(0, x)

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000

Rooms

Age

Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000

4

10

ReLU(1(4) + -100(10)) = ?

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

?

Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000

4

10

ReLU(-996) = 0

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000

4

10

0

ReLU(1(4) + -0.2(10)) = ?

?

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000
ReLU(2) = 2

4

10

0

2

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

Rooms Age Price Predicted Price Loss
4 10 $212,000
4 5 $302,000
4 0 $588,000

4

10

0

2

50000(0) + 100000(2) = ?

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

?

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000
4 0 $588,000

4

10

0

2

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

200000

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

4

5

0

3

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

300000

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

4

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

4

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

ReLU(1(4) + -100(0)) = ?

?

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

4

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

ReLU(4) = 4

4

Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

4

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

4

?

ReLU(1(4) + -0.2(0)) = ?
Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

4

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

4

4

ReLU(4) = 4
Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

4

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

4

4

?

50000(4) + 100000(4) = ?
Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000

4

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

4

4

600000

200000 + 400000 = 600000
Rooms Age Price Predicted Price Loss
4 10 $212,000 $200,000 $12,000
4 5 $302,000 $300,000 $2,000
4 0 $588,000 $600,000 $12,000

4

0

Rooms

Age

Price

-0.2

1

-100

1

50,000

100,000

ReLU

ReLU

4

4

600000

Gradient Decent

"Suppose you are at the top of a mountain, and you have to reach a lake which is at the lowest point of the mountain (a.k.a valley). A twist is that you are blindfolded and you have zero visibility to see where you are headed. So, what approach will you take to reach the lake?"

- analyticsvidhya.com

Gradient Decent

Hello Keras Demo

-Create neural network in Keras

-Train model

-Underfitting

-Epochs and batch size

-Visualize accuracy

-numPy basics

Hello Keras Demo

-Create neural network in Keras

-Train model

-Underfitting

-Epochs and batch size

-Visualize accuracy

-numPy basics

Regression Demo

- Prepare data

- Pandas

- Train/validation split

- Tuning network topology

Regression Demo

- Prepare data

- Pandas

- Train/validation split

- Tuning network topology

Binary Classifier Demo

- Overfitting

- Normalize data

- Generate training data

- Feature selection

tinyurl.com/onking

Binary Classifier Demo

- Overfitting

- Normalize data

- Generate training data

- Feature selection

Multi-Class Classifier Demo

- Encode labels

- Softmax activation

- Prediction confidence scores

Multi-Class Classifier Demo

- Encode labels

- Softmax activation

- Prediction confidence scores

Types of Problems (Recap)

Regression

Input Layer

Output Layer

Hidden Layer(s)

ReLU

ReLU

Regression

model = Sequential();
model.add(Dense(20, activation='relu', input_dim=10))
model.add(Dense(20, activation='relu'))
model.add(Dense(20, activation='relu'))
model.add(Dense(1))

model.compile(optimizer='adam', loss='mean_squared_error')

Binary Classifier

Input Layer

Output Layer

Hidden Layer(s)

ReLU

ReLU

Sigmoid

model = Sequential();
model.add(Dense(20, activation='relu', input_dim=10))
model.add(Dense(20, activation='relu'))
model.add(Dense(20, activation='relu'))
model.add(Dense(1, activation='sigmoid'))

model.compile(
    optimizer='adam', 
    loss='binary_crossentropy'
    metrics=['accuracy']
)

Binary Classifier

Multi-Class Classifier

Input Layer

Output Layer

Hidden Layer(s)

ReLU

ReLU

Softmax

Softmax

Softmax

model = Sequential();
model.add(Dense(20, activation='relu', input_dim=10))
model.add(Dense(20, activation='relu'))
model.add(Dense(20, activation='relu'))
model.add(Dense(5, activation='softmax'))

model.compile(
    optimizer='adam', 
    loss='categorical_crossentropy'
    metrics=['accuracy']
)

Multi-Class Classifier

Network Optimizing Techniques  (Recap)

Improve Data

  • Clean data
  • Get more data
  • Generate more data
  • Remove unnecessary inputs
  • Normalize data
  • Use validation split
  • Make sure test/validation data is representative of real world data

Improve Algorithm

  • Change number of layers
  • Change number of nodes in each layer
  • Change number of epochs / batch size

Takeaways

  1. Visualize everything
  2. Measure your accuracy
  3. Try things until your accuracy improves

Resources

Machine Learning Mastery

https://machinelearningmastery.com

Datacamp

Intro to Python for Data Science

Deep Learning in Python

Pandas Foundations

Rob McDiarmid

tinyurl.com/fitc-nn

@robianmcd

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