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Re: st: lincom intolerant of the variable name "d"
From
[email protected] (Jeff Pitblado, StataCorp LP)
To
[email protected]
Subject
Re: st: lincom intolerant of the variable name "d"
Date
Mon, 28 Jun 2010 15:55:33 -0500
David Airey <[email protected]> has a factor variable named 'd' in
his analysis, and is getting a syntax error from -lincom- on a simple
difference between two levels of 'd':
> After use of anova and margins, I got this error:
>
>
> . test 1.d = 2.d
>
> ( 1) 1bn.d - 2.d = 0
>
> chi2( 1) = 18.46
> Prob > chi2 = 0.0000
>
> . lincom 1.d - 2.d
> d-2: operator invalid
> r(198);
>
> And then, changing the variable name "d" to "drug", I got this:
>
> . test 1.drug = 2.drug
>
> ( 1) 1bn.drug - 2.drug = 0
>
> chi2( 1) = 18.46
> Prob > chi2 = 0.0000
>
> . lincom 1. drug - 2. drug
>
> ( 1) 1bn.drug - 2.drug = 0
>
> ------------------------------------------------------------------------------
> | Coef. Std. Err. z P>|z| [95% Conf. Interval]
> -------------+----------------------------------------------------------------
> (1) | 1.8 .4189935 4.30 0.000 .9787878 2.621212
> ------------------------------------------------------------------------------
>
> Why would the variable name "d" be a problem?
Stata is having a difficult time parsing
1.d-2.d
because 'd' is one of those special letters (like 'e') that can be used in
specifying a numeric literal. For example
1.d-2
is a way to specify .01.
We have determined where the problem is, and believe we have a fix. The fix
will be in a future executable update.
In the mean time David can use the 'i' operator, as in
. lincom i1.d - 2.d
to help Stata parse his linear combination.
--Jeff
[email protected]
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