Dear members
Am implementing the recommendations in this paper https://www.stata.com/meeting/us20/s..._Siravegna.pdf
My selection variable is sex ie select(sex) coded 0, 1.
However, when I run the model as follows:
Code:
qregsel yield age educ , select( sex ) quantile(.1 .5 .9) grid_min(-.9) grid_max(.9) grid_length(0.05)
This error keeps recurring

__000001 should be binary.
r(198);
What I doing wrong please