The line
local trial=trial2
will set the local macro trial equal to the value of the trial2 variable
from the first observation of the dataset. The equals sign and the lack of
quotes makes this a simple assignment where Stata evaluates the expression
(trial2) and comes up with trials2[1]. What you want is most likely:
local trial "trial2"
which will then substitiute the text (trial2), which is the name of a
variable, whenever it encounters `trial'. This approach should make your
equation work as expected.
Michael Blasnik
[email protected]
----- Original Message -----
From: "Cade Massey" <[email protected]>
To: <[email protected]>
Sent: Monday, November 29, 2004 3:09 PM
Subject: st: local macro vs. database variable
Can anyone tell me why the following two sub-routines would generate
different results? This code is buried in the middle of a long estimation
program. I'm trying to get away with imposing on you as little of the
program as possible -- not sure if this will be enough to tell. "trial2"
is a variable in the dataset.
Original approach:
.gen double `dum1'=$A1*(k1+k2+k3+k4)+$C1*trial2
Modified approach:
.local trial=trial2
.gen double `dum1'=$A1*(k1+k2+k3+k4)+$C1*`trial'
The original approach works fine, but I need to modify it as I write a new
program. In case it is of any help, I have one additional clue: the
residual SS is the same for both programs on Iteration 0, but grows
steadily apart after that. The modified approach provides a poorer fit
and requires more iterations to converge.
I'd guess that I'm doing tomething wrong by substituting a local macro for
a variable, but I seem to need that variable in a macro. Or maybe I
don't. Leads me to a highly related question: If I have 20 local macros
defined as `parm1' - `parm20', where the suffix indexes a "trial" variable
in the dataset, what is the best way to call those macros in my program?
If trial is a local macro, I can use:
gen double `dum1'=`parm`trial''.
But with "trial" as a variable, I haven't been able to find a syntax that
works. So I need to learn either 1) how to use a variable value as a
suffix in a local macro name, or 2) how to create a local macro that
stands in for a variable.
Thanks.
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