That can be straightforward or slightly complicated, depending on how you want to do it.
To extract the first 67 rows:
M = rand(128, 64, 1140); % Create Matrix (To Test Code)
Out = M(1:67,:,:);
To interpolate across the rows:
D1 = linspace(1, 128, 67);
Out = interp1((1:128), M, D1);
Both will produce the matrix you requested, however they are not the same.
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