edfinfo

Get information about EDF file

Description

Create an edfinfo object to get information about a European Data Format (EDF) or EDF+ file. edfinfo objects contain information such as file size, number of data records, number of signals, and number of samples.

Creation

Syntax

info = edfinfo(filename)

Description

info = edfinfo(filename) returns an edfinfo object for the EDF file specified by filename.

Input Arguments

filename — Name of EDF or EDF+ file

character vector | string scalar

Name of EDF or EDF+ file, specified as a character vector or string scalar.

Depending on the location of the file, filename can take on one of these forms.

Location	Form
Current folder or folder on the MATLAB® path	Specify the name of the file in filename. Example: 'data.edf'
File in a folder	If the file is not in the current folder or in a folder on the MATLAB path, then specify the full or relative path name. Example: 'C:\myFolder\data.edf' Example: 'myDir\myFile.ext'

Note

edfinfo does not support EyeLink^® EDF files.

Data Types: char | string

Properties

File Properties

Filename — File name

string scalar

This property is read-only.

File name, returned as a string scalar.

Example: "ecg_20200411_120.edf"

Data Types: string

FileModDate — Date last modified

string scalar

This property is read-only.

Date last modified, returned as a string scalar with the date and time the file was last modified.

Example: "11-Apr-2020 15:38:37"

FileSize — File size in bytes

integer scalar

This property is read-only.

File size in bytes, returned as an integer scalar.

Example: 4040992

Data Types: double

Header Properties

Version — Data format version

"0"

This property is read-only.

Data format version, returned as "0".

Data Types: string

Patient — Patient identification details

string scalar

This property is read-only.

Patient identification details, returned as a string scalar. Patient identification details can include their Patient ID, their sex or gender, their birth date in 'dd-MMM-yyyy' format, and their name.

Example: "X F X 120 04-JUL-1982"

Data Types: string

Recording — Recording identification details

string scalar

This property is read-only.

Recording identification details, returned as a string scalar. Recording identification details may include its start date and time, the ID of the technician that made the recording, and the ID of the equipment that made the recording.

Example: "Startdate 04-JUL-1982 X X X"

Data Types: string

StartDate — Recording start date

string scalar

This property is read-only.

Recording start date, returned as a string scalar in 'dd.MM.yy' format.

Example: "04.07.82"

Data Types: string

StartTime — Recording start time

string scalar

This property is read-only.

Recording start time, returned as a string scalar in 'HH.mm.ss' format.

Example: "17.16.37"

Data Types: string

HeaderBytes — Header size in bytes

integer scalar

This property is read-only.

Header size in bytes, returned as an integer scalar. HeaderBytes is given by (256 + NumSignals × 256) bytes. The first 256 bytes correspond to a static header and are required for all EDF and EDF+ files. The other bytes depend on the number of signals present in the data records.

Example: 2048

Data Types: double

Reserved — EDF+ interruption information

"EDF+C" | "EDF+D" | ""

This property is read-only.

EDF+ interruption information, returned as "EDF+C" or "EDF+D" for EDF+ compliant files.

• "EDF+C" — The recording is continuous: There are no interruptions and all data records are contiguous, such that the start time of each data record coincides with the start time of the previous record plus its duration.

• "EDF+D" — The recording is discontinuous with interruptions between consecutive data records.

For files that are not EDF+ compliant, this property is an empty string ("").

Data Types: string

NumDataRecords — Number of data records in file

integer scalar

This property is read-only.

Number of data records in file, returned as an integer scalar.

Note

If filename is not EDF+ compliant, NumDataRecords can be set to -1 when the number of data records is unknown. If filename is EDF+ compliant, NumDataRecords must be set to a positive integer. If filename has Reserved set to a nonempty string and NumDataRecords set to -1, edfinfo throws an error.

Data Types: double

DataRecordDuration — Duration of each data record

duration scalar

This property is read-only.

Duration of each data record, returned as a duration scalar.

Data Types: duration

NumSignals — Number of signals in file

integer scalar

This property is read-only.

Number of signals in file, returned as an integer scalar.

Data Types: double

Signal Record Properties

SignalLabels — Signal names

string vector

This property is read-only.

Signal names, returned as a string vector of length NumSignals.

["Thorax 1";"Abdomen 3"]

Data Types: string

TransducerTypes — Transducer details

string vector

This property is read-only.

Transducer details, returned as a string vector of length NumSignals. Each element of TransducerTypes contains details about the transducer used to obtain the corresponding signal in SignalLabels.

Example: ["AgAgCl electrodes";"thermistor"]

Data Types: string

PhysicalDimensions — Signal data units

string vector

This property is read-only.

Signal data units, returned as a string vector of length NumSignals. Each element of PhysicalDimensions contains the measurement units used to express the values of the corresponding signal in SignalLabels.

Example: ["uV";"mV"]

Data Types: string

PhysicalMin — Signal minimum physical value

numeric vector

This property is read-only.

Signal minimum physical value, returned as a numeric vector of length NumSignals. Each element of PhysicalMin contains the minimum physical value of the corresponding signal in SignalLabels.

Data Types: double

PhysicalMax — Signal maximum physical value

numeric vector

This property is read-only.

Signal maximum physical value, returned as a numeric vector of length NumSignals. Each element of PhysicalMax contains the maximum physical value of the corresponding signal in SignalLabels.

Data Types: double

DigitalMin — Signal minimum digital value

numeric vector

This property is read-only.

Signal minimum digital value, returned as a numeric vector of length NumSignals. Each element of DigitalMin contains the minimum digital value of the corresponding signal in SignalLabels.

Data Types: double

DigitalMax — Signal maximum digital value

numeric vector

This property is read-only.

Signal maximum digital value, returned as a numeric vector of length NumSignals. Each element of DigitalMax contains the maximum digital value of the corresponding signal in SignalLabels.

Data Types: double

NumSamples — Number of samples in signal

numeric vector

This property is read-only.

Number of samples in signal, returned as a numeric vector of length NumSignals. Each element of NumSamples contains the number of samples in the corresponding signal in SignalLabels.

Data Types: double

Prefilter — Signal data units

string vector

This property is read-only.

Signal data units, returned as a string vector of length NumSignals. Each element of Prefilter contains details about the filters, if any, used to preprocess the corresponding signal in SignalLabels.

Example: ["HP:10Hz LP:80Hz N:60Hz";"HP:0.1Hz LP:90Hz N:60Hz"]

Data Types: string

SignalReserved — Additional signal information

string vector

This property is read-only.

Additional signal information, returned as a string vector of length NumSignals. Each element of SignalReserved contains additional information, if any, about the corresponding signal in SignalLabels.

Data Types: string

Annotations — Annotations present in signal records

timetable

This property is read-only.

Annotations present in signal records, returned as a timetable containing these variables:

• Onset — Time at which the annotation occurred, expressed as a duration indicating the number of seconds elapsed since the start time of the file.

• Annotation — A string that contains the annotation text.

• Duration — A duration scalar that indicates the duration of the event described by the annotation. If the file does not specify an annotation duration, this variable is returned as NaN.

Data Types: table

Examples

Get Information About EDF File

Use the edfinfo function to create an edfinfo object containing information about the file example.edf.

info = edfinfo('example.edf')

info = 
  edfinfo with properties:

              Filename: "example.edf"
           FileModDate: "14-Apr-2020 20:55:44"
              FileSize: 31488
               Version: "0"
               Patient: "patient1"
             Recording: "Startdate not recorded"
             StartDate: "27.03.20"
             StartTime: "10.00.00"
           HeaderBytes: 768
              Reserved: ""
        NumDataRecords: 6
    DataRecordDuration: 10 sec
            NumSignals: 2
          SignalLabels: [2x1 string]
       TransducerTypes: [2x1 string]
    PhysicalDimensions: [2x1 string]
           PhysicalMin: [2x1 double]
           PhysicalMax: [2x1 double]
            DigitalMin: [2x1 double]
            DigitalMax: [2x1 double]
             Prefilter: [2x1 string]
            NumSamples: [2x1 double]
        SignalReserved: [2x1 string]
           Annotations: [0x2 timetable]

Display this information about the second signal in the file:

• Its name

• The physical units in which the data is expressed

• The minimum and maximum physical values of the data

• The number of samples it contains

nsig = 2;

disp([info.SignalLabels(nsig) info.PhysicalDimensions(nsig) ...
    info.PhysicalMin(nsig) info.PhysicalMax(nsig) info.NumSamples(nsig)])

    "ECG2"    "mV"    "-229.048"    "229.041"    "1280"

Tips

You can convert an edfinfo object to a MATLAB structure using the get function. For example:

info = edf('example.edf');
strc = get(info)

References

[1] Kemp, Bob, Alpo Värri, Agostinho C. Rosa, Kim D. Nielsen, and John Gade. “A Simple Format for Exchange of Digitized Polygraphic Recordings.” Electroencephalography and Clinical Neurophysiology 82, no. 5 (May 1992): 391–93. https://doi.org/10.1016/0013-4694(92)90009-7.

[2] Kemp, Bob, and Jesus Olivan. "European Data Format 'plus' (EDF+), an EDF Alike Standard Format for the Exchange of Physiological Data." Clinical Neurophysiology 114, no. 9 (2003): 1755–1761. https://doi.org/10.1016/S1388-2457(03)00123-8.