ankane / stl-cpp

Seasonal-trend decomposition for C++

STL C++

Seasonal-trend decomposition for C++

Installation

Add the header to your project and include it

#include "stl.hpp"

Getting Started

Decompose a time series

std::vector<float> series = {
    5.0, 9.0, 2.0, 9.0, 0.0, 6.0, 3.0, 8.0, 5.0, 8.0,
    7.0, 8.0, 8.0, 0.0, 2.0, 5.0, 0.0, 5.0, 6.0, 7.0,
    3.0, 6.0, 1.0, 4.0, 4.0, 4.0, 3.0, 7.0, 5.0, 8.0
};
size_t period = 7; // period of seasonal component

auto res = stl::params().fit(series, period);

Get the components

res.seasonal;
res.trend;
res.remainder;

Robustness

Use robustness iterations

auto res = stl::params().robust(true).fit(series, period);

Get robustness weights

res.weights;

Parameters

Set parameters

stl::params()
    .seasonal_length(7)     // length of the seasonal smoother
    .trend_length(15)       // length of the trend smoother
    .low_pass_length(7)     // length of the low-pass filter
    .seasonal_degree(0)     // degree of locally-fitted polynomial in seasonal smoothing
    .trend_degree(1)        // degree of locally-fitted polynomial in trend smoothing
    .low_pass_degree(1)     // degree of locally-fitted polynomial in low-pass smoothing
    .seasonal_jump(1)       // skipping value for seasonal smoothing
    .trend_jump(2)          // skipping value for trend smoothing
    .low_pass_jump(1)       // skipping value for low-pass smoothing
    .inner_loops(2)         // number of loops for updating the seasonal and trend components
    .outer_loops(0)         // number of iterations of robust fitting
    .robust(false);         // if robustness iterations are to be used

Strength

Get the seasonal strength

res.seasonal_strength();

Get the trend strength

res.trend_strength();

Credits

This library was ported from the Fortran implementation.

References

• STL: A Seasonal-Trend Decomposition Procedure Based on Loess
• Measuring strength of trend and seasonality

History

View the changelog

Contributing

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features

To get started with development:

git clone https://github.com/ankane/stl-cpp.git
cd stl-cpp
g++ -std=c++17 -Wall -Wextra -Werror -o test/main test/main.cpp
test/main