MATLAB: How to use sprintf with two variables with different sizes

MATLABsprintf

Hello!
I am analysing MEG data and have 20 participants with 3 blocks (called '00', '10' and '23') each, so 20×3 datasets. I want to append all these datasets with a function.
In the function, I have to manually spell out ALL the datasets that I want to append. For example:
[appendeddata] = ft_appenddata(cfg, s(1).rawdata.data00, s(1).rawdata.data10, s(1).rawdata.data23, s(2).rawdata.data00,... %and so forth
So I would have to spell out all 60 combinations, so s(1:20) and block(00,10,23). I tried to get around this by using sprinft like this:
block=["00" "10" "23"];
Subj=strings(1,20);
Subj(1:20)=1:20;
sprintf('s(%s).rawdata.data%s,',Subj,block)
But this leads to this:
ans = 's(1).rawdata.data2,s(3).rawdata.data4,s(5).rawdata.data6,s(7).rawdata.data8,s(9).rawdata.data10,s(11).rawdata.data12,s(13).rawdata.data14,s(15).rawdata.data16,s(17).rawdata.data18,s(19).rawdata.data20,s(00).rawdata.data10,s(23).rawdata.data'
How can I tell sprintf to assign the values of the first variable "Subj" to the first instance of %s, and the values of the second variable "block" to the second instance? Is that possible at all?
Thanks in advance for any answers!

Best Answer

Assuming that you have nested structures, then you can easily do something like this:
>> s(1).rawdata.data00 = 100;
>> s(1).rawdata.data10 = 110;
>> s(1).rawdata.data23 = 123;
>> s(2).rawdata.data00 = 200;
>> s(2).rawdata.data10 = 210;
>> s(2).rawdata.data23 = 223;
>> F = @(t){t.rawdata.data00,t.rawdata.data10,t.rawdata.data23};
>> C = arrayfun(F,s,'uni',0);
>> C = [C{:}];
>> V = cat(1,C{:}) % your function here!
V =
  100
  110
  123
  200
  210
  223
This simple method uses two comma-separated lists:
https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html
https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists
For your function you would simply need to call:
  ft_appenddata(cfg, C{:})
Note that your approach of using strings will lead you into writing slow, complex, buggy, obfuscated code that is hard to debug. You should always use MATLAB in terms of arrays and indices, not by trying to manipulate strings that only indirectly represent what you are trying to achieve:
https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval
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