Update multiple columns in table without loop, dot vs curly braces

Hi all,

I'd like to convert multiple columns (Variables) in a table object to another class like categorical or double. So far I have to use a loop, could this be simplified:

t = table(string(rand(3,1)),{'a';'b';'c'},{'aa';'bb';'cc'},...
          'VariableNames',{'shallBeDouble', 'shallBeCategorical1', 'shallBeCategorical2'});  
tBak = t;

catVars = {'shallBeCategorical1','shallBeCategorical2'};
for field = each(catVars)
    t.(field) = categorical(t.(field));
end

doubleVars = {'shallBeDouble'};
for field = each(doubleVars)
    t.(field) = double(t.(field));
end

disp(tBak)
disp(t)

output:

    shallBeDouble    shallBeCategorical1    shallBeCategorical2
    _____________    ___________________    ___________________
    "0.85303"        'a'                    'aa'               
    "0.62206"        'b'                    'bb'               
    "0.35095"        'c'                    'cc'  

    shallBeDouble    shallBeCategorical1    shallBeCategorical2
    _____________    ___________________    ___________________
    0.85303          a                      aa                 
    0.62206          b                      bb                 
    0.35095          c                      cc

I could use varfun to create a table or a cell of categorical values, but I can't assign them simultaneously:

 t = table(string(rand(3,1)),{'a';'b';'c'},{'aa';'bb';'cc'},...
            'VariableNames',{'shallBeDouble', 'shallBeCategorical1', 'shallBeCategorical2'});  

catVars = {'shallBeCategorical1','shallBeCategorical2'};
t(:,catVars) = varfun(@categorical, t(:,catVars))

results in

The following error occurred converting from categorical to cell:
Conversion to cell from categorical is not possible.

Can the content of a column only be changed using the dot operator? I thought this would be equal: t.{:,'var1'} and t.var1?

Thanks!

[Jan Kappen]

Shall I try to rephrase the question somehow?