How to prompt for input using an existing variable in the prompt.

Answer 1

You can use the command input for this, combined with sprintf.

%# set defaults
radius = 12.6;

%# ask for inputs
tmp = input(sprintf('Enter new radius value (R=%4.2f)\n',radius));
%# if the user hits 'return' without writing anything, tmp is empty and the default is used
if ~isempty(tmp)
    radius = tmp;
end

As an alternative, you may want to look into INPUTDLG