In the optim() function there is a syntax : res <- .Internal(optim(par, fn1, gr1, method, con, lower, Here how can I see the inside-codes of ".Internal" function ? Regards, -- View this message in context: http://www.nabble.com/How-to-look-within-.Internal---tp20581897p20581897.html Sent from the R help mailing list archive at Nabble.com.