st: r(2000) sometimes, but the data are always the same

[Pablo Mitnik <pmitnik@ssc.wisc.edu>]

Dear all,

I am running a 100-rep loop with the following code inside:


-------code begins----------------------------

ml model lf model6p_lf (alpha:mob_rate=) (beta:) (theta1:) (theta2:) 
(theta3:) (theta4:), technique (nr bfgs dfp bhhh) constraints(1)

 ml check

 ml search alpha 0 1  beta 0 70 theta1 0 1 theta2 0 1 theta3 0 1 theta4 
0 1, repeat(30)

 ml maximize, nolog

---------code ends--------------------------------


In most reps it works like a charm -- it converges in about 20-30 
iterations. But once in a while I receive the following very annoying 
message:


"r(2000) no observations."

I found the following explanation in Stata help:

"You have requested some statistical calculation and there are
no observations on which to perform it. Perhaps you specified
if  exp or  in range  and inadvertently filtered all the data."


However, given that I always use the same data, this explanation doesn't 
make a lot of sense. After all, I always use exactly the same data, and 
the error does not occur most of the time.

Any thoughts?

Pablo






--
Pablo A. Mitnik
University of Wisconsin-Madison (http://www.wisc.edu/ )
Department of Sociology ( http://www.ssc.wisc.edu/soc/)
Center on Wisconsin Strategy (http://www.cows.org/ )
1180 Observatory Drive
Room 7114A
Madison, WI 53706
TEL (608) 2621839
E-mail: pmitnik@ssc.wisc.edu


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