Standard deviation across columns

Transform the model accordingly or... you'll have to type the usual formula by hand using the column names. I told you it's tedious and in my view incorrect. If you are creating a calculated column, you'll have to do something like:

var Mean_ = ( T[Col1] + ... + T[ColN] ) / N
var Var_ = ( ( T[Col1] - Mean_ )^2 + ... + ( T[ColN] - Mean_ )^2 ) / ( N - 1 )
return
    Var_^(0.5)
 
// You know that you'll have to write out
// all the columns in the above formula
// and replace the "...", right? Told you
// it would be tedious and not scalable...