TimeBlender

A programmatic and compositional time series generator.

Introduction

TimeBlender is a programmatic compositional time series generator. By programmatic it is meant that series are specified through programming; and, by compositional, that the programming structures used to this end can be combined (or, well, blended) to achieve complex results.

This software has a dual purpose:

• to allow the author to study time series from a generative point of view, either by implementing existing concepts or researching new ones.
• and to produce artificial time series of practical interest.

On the one hand, these two objectives are antagonistic in the sense that early research might result in inadequate or not optimal ways of achieving results (i.e., because new ways are being sought, and some of these might prove pointless), which hinders practical uses. On the other hand, they are complementary in the sense that good results are not easy to achieve without good foundations, and these require research. Obviously, the present software is being developed because the latter aspect seems stronger, owing to a perception that in industrial practice we lack good synthetic time series generation. For example, while general ARMA-based generators are easy to find, the author could not locate generators for user behavior in financial applications such as banking (see model examples below).

Target applications include:

• Permit data scientists to work with artificial, but realistic, data while access to real data is not available (either because it does not exist yet, or because bureaucratic procedures create unreasonable delays).

• Data augmentation, particularly for RNN models.

• Artificial stress scenarios simulation (e.g., a market crash).

Please note that this is a very early prototype, therefore API stability cannot be guaranteed, as pretty much anything could change.

Features

Main features:

• Event-based: each time point is generated based on an event class. Several standard such events are provided, and it is easy to add more.
• Programmatic: events can be specified by arbitrary (Python) programs, hence they are not limited to traditional statistical techniques. For example, agent-based models could be defined to simulate market data.
• Compositional: events can be composed to obtain complex events.
• Pandas-based: Pandas is used in various parts to allow convenient post-generation processing options and integration with other tools.

(Even more) experimental features:

• Learning: Rudimentary and early support for learning from observations is provided through black-box parameter optimization (currently using the hyperopt library). The idea here is that one can learn from real time series in order to be able to generate similar ones automatically. The objective is not forecasting, although that might be possible eventually. At present, it is unclear how this aspect will evolve.

Standard models, which work both as examples and as a basic model library, include:

• AR, MA and ARMA.
• Seasonal effects.
• Banking behavior of salary earners.
• Kondratiev business cycle.

Please note that some of the above are provided as rather naive implementations. It is hoped that more sophisticated models take their place as the library improves.

Installation

TimeBlender is developed in Python and provided as a PIP package:

pip install time-blender

It can also be installed directly from GitHub:

pip install git+https://github.com/paulosalem/time-blender#egg=time-blender

Use

TimeBlender is designed mainly for programmatic use. However, for convenience, a command-line interface is also provided and allows access to pre-defined models.

Programmatic Use

Jupyter notebooks are provided with many examples on how to use TimeBlender. Here, let us take a look at some simple examples.

The following would generate a wave of period 30 and amplitude 3, summed with normal noise of mean 0 and standard deviation 1:

  from time_blender.core import *
  from time_blender.random_events import *
  from time_blender.deterministic_events import *
  from time_blender.coordination_events import *
  
  norm = NormalEvent(0, 1)
  we = WaveEvent(30, 3)
  
  compos = norm + we
  
  data = generate(compos, pd.Timestamp(2018, 1, 1),  pd.Timestamp(2018, 31, 1), n=1)
  
  # data contains the generated series.

Some models are predefined for convenience. For instance, a random ARMA(4, 2) model can be defined as:

  from time_blender.core import *
  from time_blender.models import ClassicModels
  
  model = ClassicModels.arma(4, 2)
  data = generate(model, pd.Timestamp(2018, 1, 1),  pd.Timestamp(2018, 31, 1), n=1)
  
  # data contains the generated series.

Command-Line Use

The PIP package installs a script named time_blender. To see the available options, models and their parameters, type:

  time_blender -h

License

MIT License

Copyright (c) 2018 Paulo Salem

Please see the attached LICENSE file for details.