parfor iel=1:tne
data((iel-1)*576+1:576*iel)=data2(iel,:);
end
That is, MATLAB can analyze literal indices in ways that it cannot do when those indices are computed.
However, unless you have good reason not to, you should simply create data as a 576 x something array and without using parfor,
data(:, 1:tne) = data2(:, 1:tne) .';
... especially if you can manage to compact it down to just
data = data2 .';
After the copying has been done with 2D indices, then it is very fast to
data = reshape(data, 1, []);
