AugmentTS :: Time Series Data Augmentation using Deep Generative Models

Note!!! The package is under development so be careful for using in production!

Basic Features

• Time Series Data Augmentation using Deep Generative Models
• Visualizing the Latent Space of Generative Models
• Time Series Forecasting using Deep Neural Networks

Installation

You can install the last stable version using pip

pip install augmentts

How to Use

Augmentation Guide

Create an augmenter

from augmentts.augmenters.vae import LSTMVAE, VAEAugmenter

# create a variational autoencoder
vae = LSTMVAE(series_len=100)
# create an augmenter
augmenter = VAEAugmenter(vae)

The above code uses the default settings for the LSTM-VAE model. You can customize its architecture or use your own model for encoder and decoder. Note currently we only support Keras models.

Train the augmenter

augmenter.fit(data, epochs=50, batch_size=32)

Generate new time series!

Two strategies for sampling have been implemented.
You can simply sample from the latent space. Here n is the number of generated series

augmenter.sample(n=1000)

You also can generate time series by reconstructing a set of series.

augmenter.sample(X=data)

In both cases you can control the variety of generated time series using sigma

augmenter.sample(n=1000, sigma=0.2)

Forecasting Guide

First we create a random dataset then use prepare_ts helper function to prepare the dataset for forecasting.

from augmentts.forecasters.deep import LSTMCNNForecaster
from augmentts.utils import prepare_ts
import numpy as np

# creating a random dataset
ts = np.random.rand(100, 10)
# preparing data for rolling window regression
X, y = prepare_ts(ts, 8, 4)

Now we can create a forecaster and train it. Note the fit function is just an alias for Keras fit function thus you can pass all of the supported arguments of Keras fit function.

model = LSTMCNNForecaster(window_size=8, steps_ahead=4, n_series=10)
model.fit(X, y, epochs=10)

After training you can use predict to evaluate the model.

model.predict(X)

Supported Augmenters

Supported models for augmentation currently are as follows:

Model	Type	Supported Time Series	Description
LSTMVAE	Variational Autoencoder	Univariate, fixed length	A Variational Autoencoder with stacked LSTM layers for encoder and decoder based on the paper [https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4009937]

Supported Forecasters

Currently an LSTM-CNN forecaster is implemented. You can either customize it or just implement your own architecture.

Examples

Augmenting ETS Time Series

Let's see how to use AugmentTS to generate time series similiar to one of the ETS families.

import matplotlib.pyplot as plt
import seaborn as sb
sb.set(style='white')
import pandas as pd

Using ETSDataset class we can sample time series from any ETS model.

from augmentts.datasets import ETSDataset

For the sake of simplicity we sample 60 series from ANA model (Additive error, No trend, Additive seasonality) and 30 seris from MNN model (Multiplicative error, no trend, no seasonality):

# sampling a few series from ETS model
ets = ETSDataset(ets_families={
    'A,N,A' : 60, # 60 samples from ANA model
    'M,N,N' : 30  # 30 samples from MNN model
}, length=100)

ts_data, family = ets.load(return_family=True)

We can use any dimensionality reduction or manifold learning method for visulizing the series in plane. Let's just use t-SNE.

from sklearn.manifold import TSNE

tsne = TSNE(n_components=2)
z = tsne.fit_transform(ts_data)

We simply use Pandas and Seaborn to draw a scatte plot

original_df = pd.DataFrame({'family' : family})
original_df[['z1', 'z2']] = z

sb.scatterplot(data=original_df, x='z1', y='z2', hue='family')

Now we use AugmentTS to augment the MNN family:

from augmentts.augmenters.vae import LSTMVAE, VAEAugmenter

# creating the VAE
vae = LSTMVAE(series_len=100, encoder_hiddens=[512, 256, 128], decoder_hiddens=[128, 256, 512])
augmenter = VAEAugmenter(vae)
# training the VAE on MNN family
vae_data = ts_data[-30:, :].reshape(-1, 1, 100)
augmenter.fit(vae_data, epochs=100, batch_size=16)

Generating 30 new time series.

n_generated = 30
generated = augmenter.sample(n=n_generated, sigma=0.5)
generated = generated.numpy()[:, 0, :]

Now we visualize the augmented time series and the original ones

z = tsne.fit_transform(np.vstack([ts_data, generated]))
augmented_df = pd.DataFrame({'family' : family + ['Generated M,N,N']*n_generated})
augmented_df[['z1', 'z2']] = z
sb.scatterplot(data=augmented_df, x='z1', y='z2', hue='family')

Here is the result of augmentation!

Using VAE for Representation Learning

VAE can be used to extract a rich representation of data. Unlike a simple AutoEncoder The features extracted by VAE are more noise-invariant and distangled. To see an example we load NN5 dataset which is included in the package:

from augmentts.datasets import NN5Dataset

nn5 = NN5Dataset()
original_data = nn5.load()

Next we create a VAE for augmentation. Since we are going to visualize the extracted features, we set latent dimension of VAE to 2.

from augmentts.augmenters.vae import LSTMVAE, VAEAugmenter

vae = LSTMVAE(series_len=original_data.shape[2], latent_dim=2)
augmenter = VAEAugmenter(vae)
augmenter.fit(original_data, epochs=100, batch_size=32)

To access the latent features you can use latent method of VAEAugmenter:

latent = augmenter.latent(original_data).numpy()

Finally, you can visualize the extracted features:

import matplotlib.pyplot as plt

plt.title('Latent Representation')
plt.scatter(latent[:, 0], latent[:, 1])

Contributors

The list of the current contributors:

• Sasan Barak
• Amirabbas Asadi
• Ehsan Mirafzali
• Mohammad Joshaghani