jARIMA

Overview

This a web application that develops an auto-ARIMA function in Java based on the article by Hyndman and Khandakar, 2008 and implementation in R.

Technology stack

The Java web application uses Springboot as the backend framework, R as the comparable analytics engine with the daemonised Rserve client to process time series data and Angular as the frontend framework. Documentation of the RESTful API service is handled by Swagger. Development is done within a Docker. Note the we also use NGINX as the a load balancing reverse proxy.

Building the application

We use Docker in development to make it easy to build, run and share. We have three Dockerfile's: one the builds the Java backend, one that sets up the Rserve client and one that builds the Angular GUI. All components of the application can be built from the build.sh file:

git clone https://github.com/O1sims/jARIMA.git
cd jARIMA
bash build.sh all

The build.sh file has multiple options to choose from.

Running the application

The build.sh file also coordinates the running of the application. Specifically, the application can be run with the following command:

bash build.sh up

Likewise, the application can be brought down with bash build.sh down.

By default, the main ARIMA application is accessible on port 80 or 3000, the API and backend components are on port 9000, and the Rserve client is run on port 6311. The docker-compose.yml can be altered to allow these services to run on different ports. Swagger API documentation can be found at localhost:9000/api/swagger-ui.html.

Environmental variables for the application can be changed in the docker-compose.yml file.

Using the application

There are two POST API endpoints are developed for this application: one that runs ARIMA analysis in R (.../api/r-arima/) and one that runs ARIMA analysis in Java (.../api/j-arima/).

Request

Both API endpoints consume the same payload structure consisting of:

• "forecastPeriod" A positive integer
• "tsData" An array of doubles (must be > 9 in length) Consider an example structure below:

{
  "forecastPeriod": 2,
  "tsData": [
    1,2,3,4,5,6,7,8,9,10,11.12
  ]
}

Response

Overall, the ARIMA API's will respond with similar outputs.

The R ARIMA endpoint produces:

• "forecast" An array of doubles relating to the point estimates
• "lowerBound" An array of doubles relating to 95% lower bound
• "upperBound" An array of doubles relating to 95% upper bound Consider an example structure below:

{
  "forecast": [
    13, 14
  ],
  "lowerBound": [
    12.5, 13.5
  ],
  "upperBound": [
    13.5, 14.5
  ]
}

The Java ARIMA endpoint produces extra data, which relate to the models goodness of fit:

• "forecast" An array of doubles relating to the point estimates
• "lowerBound" An array of doubles relating to 95% lower bound
• "upperBound" An array of doubles relating to 95% upper bound
• "rmse" Root Mean Square Error
• "aic" Akaike Information Criterion (asymptotically selects the correct model)
• "maxNormalizedVariance" Maximum normalized variance Consider an example structure below:

{
  "aic": 0,
  "forecast": [
    0
  ],
  "lowerBound": [
    0
  ],
  "maxNormalizedVariance": 0,
  "rmse": 0,
  "upperBound": [
    0
  ]
}

Accuracy

The R script written in ./analysis/R/compareARIMA.R is used to test the accuracy and time taken for the ARIMA analysis.

In terms of accuracy, the Java and R results converge as the time series data being supplied increases in size.

It is 10 to 100 times faster than the R implementation.