How can I automatically let Matlab input the file in sequence?

How can I let Matlab automatically input the file itself rather than one by one myself?

I mean, I want to put `Sample 1.wav` and then output `Sample 1.png` and then

put `Sample 2.wav` and then output `Sample 2.png` and then put `Sample 3.wav` and then output `Sample 3.png`

I do not want to type myself 1, 2, 3 and rather let the matlab run itself from `1 to 1,000`

    [y,Fs] = audioread('sample1.wav');
    spectrogram(y,'yaxis')
    saveas(gcf,'sample1.png')

Then

   [y,Fs] = audioread('sample2.wav');
    spectrogram(y,'yaxis')
    saveas(gcf,'sample2.png')

Then

    [y,Fs] = audioread('sample3.wav');
    spectrogram(y,'yaxis')
    saveas(gcf,'sample3.png')

[Roger J]

You can use a loop.

Inside of the loop body, build a string with the filename to read/write. Then use those variables when you call audioread() and saveas().

Can you try this:

>> for i=1:1000
     fn_read ="sample"+i+".wav"; % this is the file name to read from
     fn_write="sample"+i+".png"; % this is the file name to write to
     [y,Fs] = audioread(fn_read);
     spectrogram(y,'yaxis')
     saveas(gcf,fn_write)
   end

if it works for you, let me know.

[alan daniel]

Thanks. Sorry for late reply. It take me time to debug.

It have error:

Error using which
Arguments must contain a character vector.

Error in multimedia.internal.io.absolutePathForReading (line 10)
whichFileName = which(filename);

Error in audioread (line 74)
filename = multimedia.internal.io.absolutePathForReading(...

Error in Spectrogram (line 35)
     [y,Fs] = audioread("sample"+i+".wav");

I had tried to :

%%
fn_read ="sample1.wav";
[y,Fs] = audioread(fn_read);
sound(y,Fs);

It is still the same.

filename = 'sample1.wav';
[y,Fs] = audioread('sample1.wav');
sound(y,Fs);

Is working. Does audioread cannot take filename?

[Roger J]

what version of matlab are you using?

[alan daniel]

Matlab R2017b version.

[Roger J]

That's older than mine. Older versions worked a little different with strings.

Can you try the following:

>> for i=1:1000
     fn_read  ="sample"+i+".wav"; % this is the file name to read from
     fn_read  = char(fn_read);    % convert the string to a char array
     fn_write ="sample"+i+".png"; % this is the file name to write to
     fn_write = char(fn_write);   % convert the string to a char array
     [y,Fs] = audioread(fn_read);
     spectrogram(y,'yaxis')
     saveas(gcf,fn_write)
end

let me know if it works.

[Stephen23]

The simplest is to follow one of the approaches shown in the MATLAB documentation:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

[alan daniel]

Thanks. it works well!

[Roger J]

great news Alan.

What did you go with, my suggestion or did you use Stephen's solution?

If you used the solution, please mark it as the answer.

Answer 1

[Roger J]

Can you try the following:

>> for i=1:1000
     fn_read  ="sample"+i+".wav"; % this is the file name to read from
     fn_read  = char(fn_read);    % convert the string to a char array
     fn_write ="sample"+i+".png"; % this is the file name to write to
     fn_write = char(fn_write);   % convert the string to a char array
     [y,Fs] = audioread(fn_read);
     spectrogram(y,'yaxis')
     saveas(gcf,fn_write)
end

let me know if it works.

[alan daniel]

For MATLAB 2017b

[Stephen23]

Defining strings and then converting to char is rather convoluted.

It is more efficient to use sprintf, as the documentation shows:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

Answer 2

[Khaled Hamed]

for i=1:1000
[y,Fs] = audioread(['sample' num2str(i) '.wav']);
    spectrogram(y,'yaxis')
    saveas(gcf,['sample' num2str(i) '.png'])
end

[alan daniel]

This works too. Thanks.