Stata hardly ever does things one observation at a time. You mylogit
program will display the value of `a' for the first observation only each
time it is called because when you say
di "a=" `a'
Stata sees that `a' is a variable name and displays `a'[1] because that is
how it deals with -display var-, it displays the value of var[1]. If you
wanted a full listing of `a' then you should tell stata to -list `a'-.
The reason you see a varying number of values output each time is that ml
maximize needs to call your mylogit program multiple times in each iteration
to figure out the next step in the maximization process (to calculate
derivatives). You probably don't want to see a full listing of `a' for each
of these calls.
Michael Blasnik
[email protected]
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Tuesday, June 07, 2005 12:38 PM
Subject: st: MLE
Hi, everyone,
I'm wondering if anyone would be able to describe what the process is when
Stata
runs the ml maximize command. I am running Stata 8.2
In particular, in my MLE model, I have included a command to display the
contents of a temporary variable.
If Stata loops through my program one datapoint at a time, I would expect
to
seee the contents of this temporary variable for every datapoint in my
sample.
However, Stata doesn't seem to do this. In the "zero" iteration, it
displays my
variable 13 times. In the first iteration, it displays my variable 16
times. In
the second iteration, 9 times.
What is Stata doing to run this program? Thanks in advance.
Stanley
Here is my simple MLE program.
capture program drop mylogit3
program mylogit3
version 8.2
args todo b lnf
tempvar theta1 a c
mleval `theta1' = `b', eq(1)
quietly gen double `a' = exp(`theta1')/(1+exp(`theta1'))
quietly gen double `c' = 1/(1+exp(`theta1'))
di "a = " `a'
mlsum `lnf' = ln(`a'^($ML_y1) * `c'^(1-$ML_y1))
end
sort us_id
ml model d0 mylogit3 (indicator = w_rdsalperc)
ml check
ml search
ml maximize
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