Pawel, the only way to change the type of a variable in a table is to overwrite it. Assigning with t(:,vars) = ... or t{:,vars} = ... are assignments to specific elements of the table. These syntaxes have to account for the possibility that the rows subscript might also have been, for example, 2:end-1, and you certainly would not want t(2:end-1) = ... to change the type of those variables.
Your 4th way is an error simply because you must follow the dot with a reference to only one variable. Which is to say, using dot subscripting to change the type of more than one variable is going to need a loop, as in your 1st way.
It's also possible to do something like this:
strVars = <a logical expression>
t1 = t(:,~strVars);
t2 = varfun(@(s)cast(s,'double'),t,'InputVariables',strVars];
t = [t1 t2];
but you'll also have to put things back to their original order.
Is there a specific reason why that won't work for you? Generally avoiding loops in MATLAB is a good idea, but this is not really one of those cases. If it's a readability thing, you can just make a function called something like castTextVarsToNumeric that encapsulates the loop.
