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writeall

Write datastore to files

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    Syntax

    writeall(sds,outputLocation)
    writeall(sds,outputLocation,Name,Value)

    Description

    example

    writeall(sds,outputLocation)writes the data from the input datastoresdsto output files at the location specified inoutputLocation. The number of output files is the same as the number of files referenced by the datastore.

    writeall(sds,outputLocation,Name,Value)writes data with additional options specified by one or more name-value arguments. For example,'FilenameSuffix','norm'adds the descriptive text'norm'at the end of all output files.

    Examples

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    Open Live Script

    Create a signal datastore to iterate through the elements of an in-memory cell array of signal data. The array contains:

    • A sinusoidally modulated linear chirp

    • A concave quadratic chirp

    • A voltage controlled oscillator

    • A set of pulses of decreasing duration separated by regions of oscillating amplitude and fluctuating frequency with an increasing trend

    The signals are sampled at 3000 Hz.

    fs = 3000; t = 0:1/fs:3-1/fs; data = {chirp(t,300,t(end),800).*exp(2j*pi*10*cos(2*pi*2*t));...2*chirp(t,200,t(end),1000,“二次”,[],'concave');...vco(sin(2*pi*t),[0.1 0.4]*fs,fs); besselj(0,600*(sin(2*pi*(t+1).^3/30).^5));}; sds = signalDatastore(data,'SampleRate',fs);

    Create a folder calledFilesin the current folder. Write the contents of the datastore to files. List the contents of the folder. Thewriteallfunction uses theMemberNamesproperty ofsignalDatastoreto name the files and the signals in the files.

    fname ='Files'; mkdir(fname) writeall(sds,fname) dir(fname)
    . Member1.mat Member3.mat .. Member2.mat Member4.mat

    Create a datastore that points to the files inFiles. Read the data one file at a time. Compute and display the short-time Fourier transform of each signal.

    sdfs = signalDatastore(fname,'SampleRate',fs); tiledlayoutflowwhilehasdata(sdfs) nexttile [sg,nf] = read(sdfs); stft(sg,nf.SampleRate)结束

    Figure contains 4 axes objects. Axes object 1 with title Short-Time Fourier Transform contains an object of type image. Axes object 2 with title Short-Time Fourier Transform contains an object of type image. Axes object 3 with title Short-Time Fourier Transform contains an object of type image. Axes object 4 with title Short-Time Fourier Transform contains an object of type image.

    Remove theFilesdirectory you created earlier in the example.

    rmdir(fname,'s')
    Open Live Script

    Specify the path to four signals included with MATLAB®. The signals are recordings of a bird chirping, a train, a splat, and a female voice saying the word "MATLAB." The first three signals are sampled at 8192 Hz and the fourth at 7418 Hz. Create a signal datastore that points to the specified files.

    fls = ["chirp""train""splat""mtlb"]; folder = fullfile(matlabroot,"toolbox","matlab","audiovideo",append(fls,".mat")); sds = signalDatastore(folder,'SampleRateVariableName','Fs');

    Write the spectrograms of the signals to text files in the current folder using thewriteallandwriteSpectrogramfunctions.writealluses theMemberNamesproperty ofsignalDatastoreto name the files and the signals in the files. Create a datastore that points to the files in the current folder.

    writeall(sds,'.','WriteFcn',@writeSpectrogram) sdfs = signalDatastore('.');

    Read the data one file at a time. Display the spectrogram of each signal.

    tiledlayoutflowwhilehasdata(sdfs) nexttile [d,info] = read(sdfs); waterfall(d(2:end,1),d(1,2:end),d(2:end,2:end)') wtf = gca; wtf.XDir ='reverse'; view(30,45) xlabel("{\it f} (Hz)") ylabel("{\it t} (s)") [~,k] = fileparts(info.FileName); title(k)结束

    Figure contains 4 axes objects. Axes object 1 with title chirp contains an object of type patch. Axes object 2 with title mtlb contains an object of type patch. Axes object 3 with title splat contains an object of type patch. Axes object 4 with title train contains an object of type patch.

    ThewriteSpectrogramfunction computes the spectrogram of the input signal usingpspectrumand writes it to a MAT-file in the current folder. The function specifies 80% of overlap between adjoining segments, a time resolution of 0.15 second, and a spectral leakage of 0.8.

    functionwriteSpectrogram(data,info,~) [s,f,t] = pspectrum(data,info.ReadInfo.SampleRate,'spectrogram',...'TimeResolution',0.15,'OverlapPercent',80,'Leakage',0.8); d = [NaN t'; f s]; [~,q] = fileparts(info.SuggestedOutputName); save(q,"d")结束

    Input Arguments

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    Signal datastore, specified as asignalDatastoreobject. By default, whensdscontains in-memory data, thewriteallfunction writes the input data to MAT-files.

    Example:signalDatastore({randn(100,1)},'SampleRate',100)specifies a signal datastore containing one member, a random signal, sampled at 100 Hz.

    Folder location to write data, specified as a character vector or string scalar.outputLocationcan specify a full or relative path.

    Example:outputLocation = '../../dir/data'

    Example:outputLocation = "C:\Users\MyName\Desktop"

    Data Types:char|string

    Name-Value Arguments

    Specify optional pairs of arguments asName1=Value1,...,NameN=ValueN, whereNameis the argument name andValueis the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

    Before R2021a, use commas to separate each name and value, and encloseName在报价。

    Example:writeall(sds,outputLocation,'FolderLayout','flatten')

    layout of files in the output folder, specified as either'duplicate'or'flatten'.

    • 'duplicate'— Replicate the folder structure of the data that the signal datastore points to. Specify the'FolderLayout'as'duplicate'to maintain correspondence between the input and output datasets.

    • 'flatten'— Write all the files from the input to the specified output folder without any subfolders.

    'FolderLayout'does not apply whensdscontains in-memory data.

    Data Types:char|string

    Prefix to file name, specified as a character vector or string scalar.

    Thewriteallfunction adds the specified prefix to the output file names. For example, this code adds today’s date to the beginning of all output file names from the datastore.

    prefixText = string(datetime('today')) writeall(imds,'C:\myFolder','FilenamePrefix',prefixText);

    Data Types:char|string

    Suffix to file name, specified as a character vector or string scalar.

    Thewriteallfunction adds the specified suffix to the output file names. For example, this code adds the descriptive text'jpeg_70per'at the end of all output file names from the datastore.

    writeall(imds,'C:\myFolder','FilenameSuffix','jpeg_70per');

    Data Types:char|string

    Indicator to write in parallel, specified as eitherfalseortrue.

    By defaultwriteallwrites in serial. If you setUseParalleltotrue, thenwritealldivides the writing operations into separate groups and runs the groups in parallel if:

    • Parallel Computing Toolbox™ is installed.

    • An open parallel pool exists or automatic pool creation is enabled in the Parallel Preferences.

    Otherwise,writeallwrites in serial regardless of the value forUseParallel.

    Note

    Parallel writing is not supported forCombinedDatastoreobjects or datastores resulting from thetransformapplied to aCombinedDatastore.

    Data Types:logical

    Custom writing function, specified as a function handle. The specified function is responsible for creating the output files. You can use the'WriteFcn'name-value argument to transform data or write data to a file format different from the default, even ifwritealldoes not directly support the output format.

    Function Signature

    The custom writing function must accept at least three input arguments,data,writeInfo, andsuggestedOutputType.

    functionmyWriteFcn(data,writeInfo,suggestedOutputType)
    The function can also accept additional inputs, such as name-value arguments, after the first three required inputs.

    • datacontains the output of thereadmethod operating on the datastore.

    • writeInfois an object of typematlab.io.datastore.WriteInfowith fields listed in the table.

      Field Description Type
      ReadInfo The second output of thereadmethod of thesignalDatastore struct
      SuggestedOutputName A fully qualified, globally unique file name that meets the location and naming requirements string
      location The specifiedoutputLocationpassed towriteall string

    • suggestedOutputTypeis the suggested output file type.

    Example Function

    A simple write function that computes the spectrogram of the input signal usingpspectrumand writes it to a text file in the current folder using the MATLAB®functionwritematrix. The function specifies 80% of overlap between adjoining segments, a time resolution of 0.15 second, and a spectral leakage of 0.8.

    functionwriteSpectrogram(data,info,~) [s,f,t] = pspectrum(data,info.ReadInfo.SampleRate,'spectrogram',...'TimeResolution',0.15,'OverlapPercent',80,'Leakage',0.8); d = [NaN t'; f s]; [~,q] = fileparts(info.SuggestedOutputName); writematrix(d,append(q,".txt"))结束
    To usewriteSpectrogramas the writing function for thesignalDatastoreobjectsds, use this command.
    writeall(sds,'.','WriteFcn',@writeSpectrogram)

    Data Types:function_handle

    Version History

    Introduced in R2021a

    See Also

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