writeall
Description
writeall(
writes the data from the input datastore sds
,outputLocation
)sds
to output files at the
location specified in outputLocation
. The number of output files is the
same as the number of files referenced by the datastore.
writeall(
writes data with additional options specified by one or more name-value arguments. For
example, sds
,outputLocation
,Name,Value
)'FilenameSuffix','norm'
adds the descriptive text
'norm'
at the end of all output files.
Examples
Write In-Memory Signal Datastore to Files
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,'quadratic',[],'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 called Files
in the current folder. Write the contents of the datastore to files. List the contents of the folder. The writeall
function uses the MemberNames
property of signalDatastore
to name the files and the signals in the files.
fname = 'Files';
mkdir(fname)
writeall(sds,fname)
dir(fname)
. .. Member1.mat Member2.mat Member3.mat Member4.mat
Create a datastore that points to the files in Files
. Read the data one file at a time. Compute and display the short-time Fourier transform of each signal.
sdfs = signalDatastore(fname,'SampleRate',fs); tiledlayout flow while hasdata(sdfs) nexttile [sg,nf] = read(sdfs); stft(sg,nf.SampleRate) end
Remove the Files
directory you created earlier in the example.
rmdir(fname,'s')
Write Datastore Spectrograms to Files
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 the writeall
and writeSpectrogram
functions. writeall
uses the MemberNames
property of signalDatastore
to 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.
tiledlayout flow while hasdata(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) end
The writeSpectrogram
function computes the spectrogram of the input signal using pspectrum
and 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.
function writeSpectrogram(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") end
Input Arguments
sds
— Signal datastore
signalDatastore
object
Signal datastore, specified as a signalDatastore
object. By default, when sds
contains
in-memory data, the writeall
function 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.
outputLocation
— Folder location to write data
character vector | string scalar
Folder location to write data, specified as a character vector or string scalar.
outputLocation
can 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 as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is 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 enclose
Name
in quotes.
Example: writeall(sds,outputLocation,'FolderLayout','flatten')
FolderLayout
— Layout of files in output folder
'duplicate'
(default) | '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 when sds
contains in-memory data.
Data Types: char
| string
FilenamePrefix
— Prefix to file name
character vector | string scalar
Prefix to file name, specified as a character vector or string scalar.
The writeall
function 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
FilenameSuffix
— Suffix to file name
character vector | string scalar
Suffix to file name, specified as a character vector or string scalar.
The writeall
function 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
UseParallel
— Indicator to write in parallel
false
or 0
(default) | true
or 1
Indicator to write in parallel, specified as either false
or
true
.
By default writeall
writes in serial. If you set
UseParallel
to true
, then
writeall
divides 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, writeall
writes in serial regardless of the
value for UseParallel
.
Note
Parallel writing is not supported for CombinedDatastore
objects
or datastores resulting from the transform
applied to a
CombinedDatastore
.
Data Types: logical
WriteFcn
— Custom writing function
function handle
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 if writeall
does
not directly support the output format.
Function Signature
The custom writing function must accept at least three input arguments,
data
, writeInfo
, and
suggestedOutputType
.
function myWriteFcn(data,writeInfo,suggestedOutputType)
data
contains the output of theread
method operating on the datastore.writeInfo
is an object of typematlab.io.datastore.WriteInfo
with fields listed in the table.Field Description Type ReadInfo
The second output of the read
method of thesignalDatastore
struct
SuggestedOutputName
A fully qualified, globally unique file name that meets the location and naming requirements string
Location
The specified outputLocation
passed towriteall
string
suggestedOutputType
is the suggested output file type.
Example Function
A simple write function that computes the spectrogram of the input signal using
pspectrum
and writes it to a text file in the current folder using the
MATLAB® function writematrix
. The function specifies 80% of overlap between adjoining
segments, a time resolution of 0.15 second, and a spectral leakage of
0.8.
function writeSpectrogram(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")) end
writeSpectrogram
as the writing function for the signalDatastore
object sds
, use this
command.writeall(sds,'.','WriteFcn',@writeSpectrogram)
Data Types: function_handle
Version History
Introduced in R2021a
See Also
MATLAB 명령
다음 MATLAB 명령에 해당하는 링크를 클릭했습니다.
명령을 실행하려면 MATLAB 명령 창에 입력하십시오. 웹 브라우저는 MATLAB 명령을 지원하지 않습니다.
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