partition

Partition datastore and return on partitioned portion

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Syntax

subADS = partition(ADS,numPartitions,index)
subADS = partition(ADS,'Files',index)
subADS = partition(ADS,'Files',filename)

Description

subADS = partition(ADS,numPartitions,index) partitions datastore ADS into the number of parts specified by numPartitions and returns the partition corresponding to the index.

example

subADS = partition(ADS,'Files',index) partitions the datastore by files and returns the partition corresponding to the file of index index in the Files property.

example

subADS = partition(ADS,'Files',filename) partitions the datastore by files and returns the partition corresponding to the file specified by filename.

Examples

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Open Live Script

Specify the file path to the audio samples included with Audio Toolbox™. Create an audio datastore that points to the specified folder.

folder = fullfile(matlabroot,'toolbox','audio','samples');
ADS = audioDatastore(folder)
ADS = 
  audioDatastore with properties:

                       Files: {
                              ' .../matlab/toolbox/audio/samples/Ambiance-16-44p1-mono-12secs.wav';
                              ' .../matlab/toolbox/audio/samples/AudioArray-16-16-4channels-20secs.wav';
                              ' .../toolbox/audio/samples/ChurchImpulseResponse-16-44p1-mono-5secs.wav'
                               ... and 36 more
                              }
                     Folders: {
                              ' .../Bdoc25b.2988451/build/runnable/matlab/toolbox/audio/samples'
                              }
    AlternateFileSystemRoots: {}
              OutputDataType: 'double'
           OutputEnvironment: 'cpu'
                      Labels: {}
      SupportedOutputFormats: ["wav"    "flac"    "ogg"    "opus"    "mp3"    "mp4"    "m4a"]
         DefaultOutputFormat: "wav"

Partition the datastore into three parts.

subADS1 = partition(ADS,3,1)
subADS1 = 
  audioDatastore with properties:

                       Files: {
                              ' .../matlab/toolbox/audio/samples/Ambiance-16-44p1-mono-12secs.wav';
                              ' .../matlab/toolbox/audio/samples/AudioArray-16-16-4channels-20secs.wav';
                              ' .../toolbox/audio/samples/ChurchImpulseResponse-16-44p1-mono-5secs.wav'
                               ... and 10 more
                              }
                     Folders: {
                              ' .../Bdoc25b.2988451/build/runnable/matlab/toolbox/audio/samples'
                              }
    AlternateFileSystemRoots: {}
              OutputDataType: 'double'
           OutputEnvironment: 'cpu'
                      Labels: {}
      SupportedOutputFormats: ["wav"    "flac"    "ogg"    "opus"    "mp3"    "mp4"    "m4a"]
         DefaultOutputFormat: "wav"


subADS2 = partition(ADS,3,2)
subADS2 = 
  audioDatastore with properties:

                       Files: {
                              ' .../matlab/toolbox/audio/samples/JetAirplane-16-11p025-mono-16secs.wav';
                              ' .../runnable/matlab/toolbox/audio/samples/Laughter-16-8-mono-4secs.wav';
                              ' .../matlab/toolbox/audio/samples/MainStreetOne-16-16-mono-12secs.wav'
                               ... and 10 more
                              }
                     Folders: {
                              ' .../Bdoc25b.2988451/build/runnable/matlab/toolbox/audio/samples'
                              }
    AlternateFileSystemRoots: {}
              OutputDataType: 'double'
           OutputEnvironment: 'cpu'
                      Labels: {}
      SupportedOutputFormats: ["wav"    "flac"    "ogg"    "opus"    "mp3"    "mp4"    "m4a"]
         DefaultOutputFormat: "wav"


subADS3 = partition(ADS,3,3)
subADS3 = 
  audioDatastore with properties:

                       Files: {
                              ' .../matlab/toolbox/audio/samples/RockGuitar-16-44p1-stereo-72secs.wav';
                              ' .../matlab/toolbox/audio/samples/RockGuitar-16-96-stereo-72secs.flac';
                              ' .../matlab/toolbox/audio/samples/SingingAMajor-16-mono-18secs.ogg'
                               ... and 10 more
                              }
                     Folders: {
                              ' .../Bdoc25b.2988451/build/runnable/matlab/toolbox/audio/samples'
                              }
    AlternateFileSystemRoots: {}
              OutputDataType: 'double'
           OutputEnvironment: 'cpu'
                      Labels: {}
      SupportedOutputFormats: ["wav"    "flac"    "ogg"    "opus"    "mp3"    "mp4"    "m4a"]
         DefaultOutputFormat: "wav"
Open Live Script

Specify the file path to the audio samples included with Audio Toolbox™. Create an audio datastore that points to the specified folder.

folder = fullfile(matlabroot,'toolbox','audio','samples');
ADS = audioDatastore(folder);

Get the default number of partitions for ADS.

n = numpartitions(ADS);

Partition the datastore into the default number of partitions and return the datastore corresponding to the first partition.

subADS = partition(ADS,n,1);

Read the data in subADS.

while hasdata(subADS)
    data = read(subADS);
end
Open Live Script

Specify the file path to the audio samples included with Audio Toolbox™. Create an audio datastore that points to the specified folder.

folder = fullfile(matlabroot,'toolbox','audio','samples');
ADS = audioDatastore(folder);

Partition the datastore by files and return the part corresponding to the second file. subds contains one file.

subds = partition(ADS,'Files',2)
subds = 
  audioDatastore with properties:

                       Files: {
                              ' .../matlab/toolbox/audio/samples/AudioArray-16-16-4channels-20secs.wav'
                              }
                     Folders: {
                              ' .../Bdoc25b.2988451/build/runnable/matlab/toolbox/audio/samples'
                              }
    AlternateFileSystemRoots: {}
              OutputDataType: 'double'
           OutputEnvironment: 'cpu'
                      Labels: {}
      SupportedOutputFormats: ["wav"    "flac"    "ogg"    "opus"    "mp3"    "mp4"    "m4a"]
         DefaultOutputFormat: "wav"

This example uses:

Open Live Script

Partition a datastore to facilitate parallel access over the available parallel pool of workers.

Specify the file path to the audio samples included with Audio Toolbox™. Create an audio datastore that points to the specified folder.

folder = fullfile(matlabroot,'toolbox','audio','samples');
ADS = audioDatastore(folder);

Return an estimate for a reasonable number of partitions for parallel processing, given the current parallel pool.

pool = gcp;
n = numpartitions(ADS,pool);

Partition the audio datastore and read the data in each part.

parfor ii = 1:n
    subds = partition(ADS,n,ii);
    while hasdata(subds)
        data = read(subds);
    end
end

Input Arguments

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Audio datastore, specified as an audioDatastore object.

Number of partitions, specified as a positive integer. Use numpartitions to estimate a reasonable value for numPartitions.

Data Types: double

Index of sub-datastore, specified as a positive integer in the range [1,numPartitions].

Data Types: double

File name, specified as a character vector.

The value of filename must match exactly the file name contained in the Files property of the datastore.

Data Types: char

Output Arguments

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Output audio datastore, returned as an audioDatastore object.

Version History

Introduced in R2018b

See Also

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