# Airline Passenger Prediction using RNN – LSTM

## Prediction of number of passengers for an airline using LSTM

In this project we are going to build a model to predict the number of passengers in an airline. To do so we are going to use `Recurrent Neural Networks`

, more precisely `Long Short Term Memory`

.

### Recurrent Neural Network

- Neural Networks are set of algorithms which closely resembles the human brain and are designed to recognize patterns.
- Recurrent Neural Network is a generalization of feedforward neural network that has an internal memory.
- RNN is recurrent in nature as it performs the same function for every input of data while the output of the current input depends on the past one computation.
- After producing the output, it is copied and sent back into the recurrent network. For making a decision, it considers the current input and the output that it has learned from the previous input.
- In other neural networks, all the inputs are independent of each other. But in RNN, all the inputs are related to each other.

### Long Short Term Memory

- Long Short-Term Memory (LSTM) networks are a modified version of recurrent neural networks, which makes it easier to remember past data in memory.
- Generally LSTM is composed of a cell (the memory part of the LSTM unit) and three “regulators”, usually called gates, of the flow of information inside the LSTM unit: an input gate, an output gate and a forget gate.
- Intuitively, the cell is responsible for keeping track of the dependencies between the elements in the input sequence.
- The input gate controls the extent to which a new value flows into the cell, the forget gate controls the extent to which a value remains in the cell and the output gate controls the extent to which the value in the cell is used to compute the output activation of the LSTM unit.
- The activation function of the LSTM gates is often the logistic sigmoid function.
- There are connections into and out of the LSTM gates, a few of which are recurrent. The weights of these connections, which need to be learned during training, determine how the gates operate.

### Dataset

This dataset provides monthly totals of a US airline passengers from 1949 to 1960. The dataset has 2 columns `month`

and `passengers`

. `month`

contains the month of the year and `passengers`

contains total number of passengers travelled on that particular month.

You can download the dataset from here.

We are going to use `tensorflow`

to build the LSTM. You can install `tensorflow`

by running this command. If you machine has a GPU you can use the second command.

**!pip install tensorflow**

**!pip install tensorflow-gpu**

The necessary python libraries are imported here-

`numpy`

is used to perform basic array operations`pyplot`

from matplotlib is used to visualize the results`pandas`

for loading and manipulating the data.`Tensorflow`

is used to build the neural network- We have even imported all the layers required to build the model from
`keras`

.

importnumpyasnpimportmatplotlib.pyplotaspltimportpandasaspdfromtensorflow.keras.modelsimportSequentialfromtensorflow.keras.layersimportDense, LSTMfromsklearn.preprocessingimportMinMaxScaler

Now we will read the dataset using `read.csv()`

. We will only retain the `passengers`

column from the dataset and `reshape`

it by converting it into a `numpy array`

.

dataset = pd.read_csv('AirPassengers.csv') dataset = dataset['#Passengers'] dataset = np.array(dataset).reshape(-1,1) dataset[:10]

array([[112], [118], [132], [129], [121], [135], [148], [148], [136], [119]], dtype=int64)

Now we will plot the dataset. We can observe that the number of passengers has increased linearly.

plt.plot(dataset)

Neural networks work better if inputs are between 0 and 1. So we are going to scale down the inputs using `MinMaxScaler()`

. We can see that after scaling the minimum value is 0 and maximum value is 1.

scaler = MinMaxScaler() dataset = scaler.fit_transform(dataset) dataset.min(),dataset.max()

(0.0, 1.0)

We are going to use the data of first `100`

months as `training data`

and the last `44`

months as `testing data`

.

train_size = 100 test_size = 44 train = dataset[0:train_size, :] train.shape

(100, 1)

test = dataset[train_size:144, :] test.shape

(44, 1)

### Create training and testing dataset

We are going to predict the (i)th value in the dataset on the basis of (i-1)th value. That means we are going to look back by 1 to predict the next value. Hence we are creating a function `get_data()`

to create `dataX`

and `dataY`

for the `training`

as well as the `testing`

data.

defget_data(dataset, look_back): dataX, dataY = [], []foriinrange(len(dataset)-look_back-1): a = dataset[i:(i+look_back), 0] dataX.append(a) dataY.append(dataset[i+look_back, 0])returnnp.array(dataX), np.array(dataY) look_back = 1 X_train, y_train = get_data(train, look_back) X_train[:10]

array([[0.01544402], [0.02702703], [0.05405405], [0.04826255], [0.03281853], [0.05984556], [0.08494208], [0.08494208], [0.06177606], [0.02895753]])

y_train[:10]

array([0.02702703, 0.05405405, 0.04826255, 0.03281853, 0.05984556, 0.08494208, 0.08494208, 0.06177606, 0.02895753, 0. ])

Now we have called `get_data()`

to create the `testing data`

.

X_test, y_test = get_data(test, look_back)

Now we are going to reshape our data and make it 2 dimensional using `reshape()`

.

X_train = X_train.reshape(X_train.shape[0], X_train.shape[1], 1) X_test = X_test.reshape(X_test.shape[0], X_test.shape[1], 1)

X_train.shape

(98, 1, 1)

### Build the model

Our sequential model has 2 layers

#### LSTM layer:

This is the main layer of the model and has `5 units`

. It learns long-term dependencies between time steps in time series and sequence data. `input_shape`

contains the shape of input which we have to pass as a parameter to the first layer of our neural network.

#### Dense layer:

Dense layer is the regular deeply connected neural network layer. It is most common and frequently used layer. We have number of `units`

as 1 because we are going to get a single value as the output.

model = Sequential() model.add(LSTM(5, input_shape = (1, look_back))) model.add(Dense(1)) model.compile(loss = 'mean_squared_error', optimizer = 'adam')

We have compliled the model. We can see the summary using `model.summary()`

.

model.summary()

Model: "sequential" _________________________________________________________________ Layer (type) Output Shape Param # ================================================================= lstm (LSTM) (None, 5) 140 _________________________________________________________________ dense (Dense) (None, 1) 6 ================================================================= Total params: 146 Trainable params: 146 Non-trainable params: 0 _________________________________________________________________

After compiling the model we will now train the model using `model.fit()`

on the training dataset. We will use 50 `epochs`

to train the model. An epoch is an iteration over the entire x and y data provided. `batch_size`

is the number of samples per gradient update i.e. the weights will be updates after every training example.

model.fit(X_train, y_train, epochs=50, batch_size=1) Epoch 45/50 98/98 [==============================] - 0s 2ms/sample - loss: 0.0022 Epoch 46/50 98/98 [==============================] - 0s 2ms/sample - loss: 0.0021 Epoch 47/50 98/98 [==============================] - 0s 2ms/sample - loss: 0.0021 Epoch 48/50 98/98 [==============================] - 0s 2ms/sample - loss: 0.0021 Epoch 49/50 98/98 [==============================] - 0s 2ms/sample - loss: 0.0022 Epoch 50/50 98/98 [==============================] - 0s 2ms/sample - loss: 0.0021

Now we will test our model using `X_test`

.

y_pred = model.predict(X_test)

This is the `scaler`

value which we had used earlier.

scaler.scale_

array([0.0019305])

We had scaled down the values in our dataset before passing it to the neural network. Now we will have to get the original values back. For this we will use `scaler.inverse_transform()`

.

y_pred = scaler.inverse_transform(y_pred) y_test = np.array(y_test) y_test = y_test.reshape(-1, 1) y_test = scaler.inverse_transform(y_test)

Now we will visualize the result by plotting the real values and the predicted values.

# plot baseline and predictionsplt.figure(figsize=(14,5)) plt.plot(y_test, label = 'Real number of passengers') plt.plot(y_pred, label = 'Predicted number of passengers') plt.ylabel('# passengers') plt.legend() plt.show()

As we can see that the actual results and the predicted results are following the same trend. Our model is predicting the number of passengers with a good accuracy.

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