How to Access Avro Files with MATLAB

How to import Avro files into MATLAB

Avro files can be read directly in MATLAB using the Java library distributed by Mathworks.
Please note that the latest version matlab-avro-interface returns some errors while parsing the schema.

This guide to correctly open Avro files in MATLAB only works with matlab-avro-interface version 0.8.3

Requirements

• Java JDK8 or higher
• Maven
  • Follow the instructions in the README.txt file to install it
• Matlab-Avro interface v0.8.3

  • Version 0.8.3 can be downloaded directly from GitHub, or cloned by running the following command in the terminal:

    git clone -b v0.8.3 --recursive https://github.com/mathworks-ref-arch/matlab-avro

Post-Installation patch

To set up the library to read Empatica's Avro files, the Avro version in the pom file needs to be updated with the following steps:

1. Navigate to the repository folders and identify the pom.xml file. You should find it inside matlab-avro/Software/Java path
2. Open pom.xml and change the value of avro.version to 1.11.0 (line 16)

3. Open a terminal in the folder where pom.xml is stored and run:

   mvn dependency:copy

4. Once it has finished, the message “Build success” should appear

Configure Matlab

If you want to install the matlab-avro library only temporarily (you have to repeat this procedure every time you re-open MATLAB) simply open MATLAB and run the startup.m script, found in matlab-avro/Software/MATLAB.

If you want to install the library permanently follow these steps:

1. If you don’t have it yet, create a file named javaclasspath.txt in your prefdir folder. To know your prefidir folder, run the command prefdir in MATLAB
2. Open javaclasspath.txt and write inside the path to the .jar file of the matlab-avro library (located in .../matlab-avro/Software/MATLAB/lib/jar). Then save the file.
   Your javaclasspath.txt should look like: .../matlab-avro/Software/MATLAB/lib/jar/matlabavro-0.3.jar
3. Add the matlab-avro/Software/MATLAB/app/system folder to your MATLAB path (From MATLAB Home > Set Path > add the folder and save) and then restart MATLAB

The Java library needs to be configured either per-instance, running the startup.m script with each MATLAB instance - or permanently, by configuring javaclasspath.txt

Read an Avro file

To read Empatica’s Avro files, run the following two commands:

myReader = matlabavro.DataFileReader(PATH_TO_AN_AVRO_FILE); myReaderData = myReader.next();

myReaderData will be a MATLAB struct containing the content of the parsed Avro file.

(replace PATH_TO_AN_AVRO_FILE with the path of an Avro file)