Maximum likelihood estimation - invalid name error

[Stefano Pagliarani]

Hello everyone,
I keep on getting invalid name errors with this code for a maximum likelihood estimation.

program define normal
version 16.1
args lnf mu sigma
quietly replace `lnf'=ln(normd(($ML y1-'mu')/'sigma'))-
ln('sigma')
end

Any idea what it can be?

Stefano

[Sebastian Kripfganz]

Replace 'mu' by `mu' and similarly 'sigma' by `sigma'. (Note the difference in the opening single quote.) Also, make sure to not put the ln(`sigma') term on a new line.

[Stefano Pagliarani]

Thank you very much!