Resolve readChannelGroups out of Bounds when combining multiple .tdms files

I have multiple tdms files which I am trying to combine into one using the information available at https://uk.mathworks.com/help/daq/example-merge-multiple-tdms-files.html

When I use this code I get the following error:

readChannelGroups out of Bounds. startIndex(0) + readSize(52417) <= max(numSamplesAcrossChannelGroups)(52276)

From this I gather that there is a limit on the number of rows that can be read, which has been set to 52276. This is the number of rows in the first file in the DataStore. The code runs until it meets a file larger than the first, with 52417 rows.

I tried to remedy this by setting tdmsDatastore ReadSize to 51000 but then I get this error:

readChannelGroups out of Bounds. startIndex(51000) + readSize(1417) <= max(numSamplesAcrossChannelGroups)(52276)

Is there a way I can combine multiple tdms files into one tdms file where it doesn't matter if the files are different lengths?

Here is my full code. If anyone has a suggestion as to how to share the tdms data (or minimal data) in a sensible way then it is welcome!

foldername = uigetdir();

 % move up one folder by removing the last bit of the foldername and
 % assigning that to variable called "f"
f = foldername(1:end-10);
cd(f);

id = foldername(end-8:end); % new filename = final 9 chars of folder name
newfilename = [id '.tdms'];

ds = tdmsDatastore(foldername, ReadSize = "file");

data = readall(ds);
tdmswrite(newfilename, data);

while(hasdata(ds))
    data = read(ds); %read one file.
    tdmswrite(newfilename, data);
end

clear

Answer 1

[Aylin]

Hello Eleanor, this is likely to be a bug in tdmsDatastore. I have forwarded this to the tdmsDatastore developers.

As a workaround, can you replace this loop:

ds = tdmsDatastore(foldername, ReadSize="file")

while(hasdata(ds))
    data = read(ds)
    tdmswrite(newfilename, data);
end

With something like this?

fileSet = matlab.io.datastore.FileSet(foldername, FileExtensions=".tdms");

while(fileSet.hasNextFile())
    data = tdmsread(fileSet.nextfile().Filename)
    tdmswrite(newfilename, data);
end

I hope this helps!

Rylan

[Eleanor Hassan]

Thank you so much Rylan! This has completely resolved my problem.

For anyone looking in the future, here is the entirety of the working code:

foldername = uigetdir();

f = foldername(1:end-10);
cd(f);

id = foldername(end-8:end)
newfilename = [id '.tdms'];

fileSet = matlab.io.datastore.FileSet(foldername, FileExtensions=".tdms");

while(fileSet.hasNextFile())
    data = tdmsread(fileSet.nextfile().Filename)
    tdmswrite(newfilename, data);
end

clear