It's pretty awkward if there is no pattern to the naming of the variables, so if you can fix the naming problem upstream, you should try to do that. If you can't, then one approach is to define a function that takes a variable number of arguments, and does the mean of each one:
function arrayOfMeans = getMeans(varargin)
arrayOfMeans = zeros(nargin,1);
for n=1:nargin
arrayOfMeans(n) = mean(varargin{n}(:)); % Calculating means of all elements in array
end
end
Then call that function with the list of your variables as the input. For example,
>> getMeans(magic(3),rand(7),eye(4))
In your case, you would do
>> getMeans(A,D,R,T)
etc
