I need to combine two channels of cell arrays into a single matrix for processing. The two channels should be the same size but in some cases not - how can I change the size?

channelData = cell(2, 1);

........

I have tried code like this but it states the concatenation dimesnions are inconsistent:

% Ensure both channels have the same number of samples
numSamplesCh1 = length(channelData{1});
numSamplesCh2 = length(channelData{2});

if numSamplesCh1 > numSamplesCh2
    numSamplesCh1 = numSamplesCh2;
    mycell = trimdata(channelData,numSamplesCh1);
else
    numSamplesCh2 = numSamplesCh1;
    mycell = trimdata(channelData,numSamplesCh2);
end

combinedData = [channelData{1}, channelData{2}];

The above code combines the channels but in some cases they are wrong size. How can I resize the ChannelData{1} and ChannelData{2} so they are the smallest size of the two (please)?

Answer 1

[Voss]

Assuming that channelData is a 2-element cell array, that channelData{1} and channelData{2} are both column vectors, and you want to combine them into a matrix with two columns, then you can use trimdata to do so like this:

% n: length of shorter vector
% idx: index (1 or 2) of shorter vector in channelData
[n,idx] = min([numel(channelData{1}) numel(channelData{2})]);

% trim the longer vector (3-idx makes 1 become 2 and vice versa) to length n
channelData{3-idx} = trimdata(channelData{3-idx},n);

% combine the vectors into an n-by-2 matrix
combinedData = [channelData{:}];

If you don't want to overwrite channelData, then use a temporary variable instead:

tmp = channelData;

tmp{3-idx} = trimdata(tmp{3-idx},n);

combinedData = [tmp{:}];

Your mistake was using trimdata to trim the cell array channelData itself rather than the contents of one of its cells (i.e., channelData{1} or channelData{2}, whichever is longer). That and not using the assigned output mycell, so that you were not actually modifying channelData at all before attempting to concatenate its contents.

[James Griffin]

Thank you Voss for your indepth answer - This is what happens when you come in and out of coding for long periods of time........you become very rusty! ;-) Maths and languages are the same!

I really do appreicate the long, indepth answer as it has helped me a lot.

Ultinmately, thank you for your selfless attitude it is most appreciated! Have a great day to day.

Kind regards,

James

[Voss]

You're welcome!