Dear all,

I have been running a non-linear regression on a data-set using the following specification: nl(price={a1}*log(1-({a2}+{a3}*post_int)*exp(-{a4}*lease_maturity))+{c})

However, the output I am getting isn't displaying any of the coefficients and says (constrained). I am not sure why this problem is occurring and its the first time that I am facing this issue while running a non-linear regression.


. nl(price={a1}*log(1-({a2}+{a3}*post_int)*exp(-{a4}*lease_maturity))+{c})
(obs = 375,537)

Iteration 0: residual SS = 85165.89
Iteration 1: residual SS = 85165.89


Source | SS df MS
-------------+---------------------------------- Number of obs = 375,537
Model | 8.600e-09 0 . R-squared = 0.0000
Residual | 85165.892 375536 .226784895 Adj R-squared = 0.0000
-------------+---------------------------------- Root MSE = .4762194
Total | 85165.892 375536 .226784895 Res. dev. = 508522.6

------------------------------------------------------------------------------
price | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
/a1 | 0 (constrained)
/a2 | 0 (constrained)
/a3 | 0 (constrained)
/a4 | 0 (constrained)
/c | 9.127679 .0007771 11745.72 0.000 9.126155 9.129202
------------------------------------------------------------------------------
Parameter c taken as constant term in model & ANOVA table

Could anyone shed light on why I might be getting such a result?

Thank you!