Hi all,

I am trying to estimate the parameter delta using the nl command in Stata 15.1, as follows:

nl (depvar=ln(1+sum(var1/(var2^{delta})))), in(delta .05).

The command works fine, but returns a negative value. The problem is, the intuition of the model requires that delta be constrained between 0 and 1. I cannot find a way to constrain the parameter using the nl command. Does anyone have suggestions as to how I could constrain and estimate the parameter?

Note: I have altered the initial value significantly, but continue to get a negative estimate.

Best,

Adam