Return of the gradient function when using Optim functions and colSums

Dear,

i am using the programming of the package "sampleSelection" for a study and
I do not understand the error of my simulation, I posted the detailed doubt
in stackoverflow! Link below:

http://stackoverflow.com/questions/41404416/return-of-the-gradient-function-when-using-optim-functions-and-colsums


Thank you!

best regards,

Fernando de Souza Bastos
Teacher of Mathematics and Statistics

Universidade Federal de Vi?osa (UFV)

Campus UFV - Florestal

PhD in progress in Statistics
Universidade Federal de Minas Gerais (UFMG)