Sleep EDFx Toolbox

A toolbox to download, extract, load and view signals from the PhysioNet Sleep EDF Expanded Database.

This work is part of the research performed at the Rodriguez-Villegas Lab, Imperial College London, UK.

##Citations##

Please cite the following publication when using this toolbox:

For this toolbox:

Imtiaz, S.A.; Rodriguez-Villegas, E., "An Open-source Toolbox For Standardized Use Of PhysioNet Sleep EDF Expanded Database," in Engineering in Medicine and Biology Society (EMBC), 2015 37th Annual International Conference of the IEEE, 2015

Standard PhysioNet citation:

Goldberger AL, Amaral LAN, Glass L, Hausdorff JM, Ivanov PCh, Mark RG, Mietus JE, Moody GB, Peng C-K, Stanley HE. PhysioBank, PhysioToolkit, and PhysioNet: Components of a New Research Resource for Complex Physiologic Signals. Circulation 101(23):e215-e220 [Circulation Electronic Pages; http://circ.ahajournals.org/cgi/content/full/101/23/e215]; 2000

BioSig citation for EDF files conversion:

Vidaurre, Carmen, Tilmann H. Sander, and Alois Schlögl. "BioSig: the free and open source software library for biomedical signal processing." Computational intelligence and neuroscience 2011 (2011).

##Features##

• Download the complete set of 61 recordings
• Extract the EDF files and convert them to Matlab signals
• Get Matlab-compatible hypnogram from the annotations
• Extract overnight sleep data and hypnogram from consistent start and end times
• View signals between any time along with its hypnogram
• Compute performance results
• Use RK or AASM classification

Installation

• Download or clone the repository and add it to your path
• IMPORTANT: For EDF to Matlab conversion, BioSig Toolbox is required and its installation must be on the search path. Just download the MATLAB version and run the installer.

##Usage##

All-in-one: download EDF files, annotations, extract data and process hypnograms

This is the simplest method to get started with the PhysioNet Sleep EDF Expanded database.

initialSetupEDFx(destination_directory)

• destination_directory is an optional argument to specify location for download

This function is needed only for the first time to get all the needed data and set up your working area with all the tests arranged in separate folders from where they can be loaded. Each test will be in a sub-directory inside the destination_directory and each newly created test_directory will have the source edf file, matlab folder with signals in .m files and an info folder with sampling frequency, list of channels and other annotations.

Loading a test

[data, f_samp, number_of_epochs, hypnogram, times] = loadEDFx(test_dir, classification_mode)

• Specify the top level test_dir of the test to be loaded. For example, C:\Full_Path\ST7120
• classification_mode to use can be either 'RK' or 'AASM'

The function returns the following:

• data is a container (dictionary) with all channels/signals in the test.
• Use data.keys to get a list of all available channels.
• To work with a particular channel's data, for example, fpz-cz you can load it as data('eeg_fpz')
• f_samp is the sampling frequency
• number_of_epochs is the number of 30-second epochs in the test (for overnight sleep)
• hypnogram is the corresponding hypnogram for each 30-s epoch in the loaded data
• times is a vector containing the start and end times of the test recording

Please refer to the following publication on how the starting and end times are calculated which in turn influence the total number of epochs. The publication also details the hypnogram conversion from RK to AASM.

Recommendations for performance assessment of automatic sleep staging algorithms, SA Imtiaz and E Rodriguez-Villegas, Engineering in Medicine and Biology Society (EMBC), 2014 36th Annual International Conference of the IEEE.

Viewing signals for a test

viewEDFxSignals(signal, times, start_time, end_time, f_samp, hypnogram)

• signal is any signal from the data container above. Only one signal can be passed here
• times is the reference obtained from above to determine original start and end times
• start_time is the time in hh:mm:ss format from where the signal is to be plotted
• end_time is the time in hh:mm:ss format up to which the signal is to be plotted
• f_samp is the sampling frequency
• hypnogram as obtained from loadEDFx function

Compute performance metrics

computeEDFxPerformance(test_hypnogram, ref_hypnogram, classification_mode)

• test_hypnogram is a Matlab vector with labels for each 30-s epoch
• ref_hypnogram is the reference obtained from loadEDFx function
• classification_mode can be either 'AASM' or 'RK'
• The test_hypnogram must conform to the same format as ref_hypnogram and use a single character to describe a sleep stage for each epoch. There are 'W','R','1','2','3' for AASM and includes 'M' and '4' for RK classification mode. An additional 'X' may be used for unknown stages.

Other functions

The following functions are bundled in the initialSetupEDFx() function but can be called upon separately if needed.

Downloading EDF files for all tests

[saved_file, status] = downloadEDFxData( )
[saved_file, status] = downloadEDFxData(destination_directory)

• saved_file is the full path of the downloaded EDF file
• status corresponds to the success/failure of each file (it's download status)
• destination_directory is an optional argument to specify location for download

Downloading annotations for all tests

downloadEDFxAnnotations( )
downloadEDFxAnnotations(destination_directory)

• destination_directory is an optional argument to specify location for download

Convert EDF files to Matlab

convertEDFxToMat(saved_file, status)

• saved_file is the full path of the downloaded EDF file
• status corresponds to the success/failure of each file (it's download status) and should not be 0 which indicates a failed download when used in the workflow
• The converted files are stored within the test directory
• This function requires the presence of BioSig Toolbox toolbox available on the search path

Process hypnogram annotations

hypnogram = processEDFxHypnogram(hyp_file)

• hyp_file is the annotations file with all sleep stages and their corresponding duration obtained from PhysioNet
• hypnogram contains a Matlab vector for labels corresponding to sleep stages for each 30-second epoch

Issues

For any issues or bug reports please use GitHub Issues

Contribute

Submit pull requests

Contact

• Visit our research group website to know more about our work: http://www.imperial.ac.uk/rodriguez-villegas-lab
• Contact me at [email protected]

License

© Syed Anas Imtiaz | 2015 | MIT License – http://opensource.org/licenses/MIT