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Re: st: marginsplot after xtmixed with square term


From   Scott Merryman <scott.merryman@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: marginsplot after xtmixed with square term
Date   Wed, 13 Mar 2013 21:16:51 -0500

The first i.pressure term was superfluous.

Terms like   c.repl##c.repl mean repl repl*repl

 c.repl##c.repl##i.pressure  is the same as repl i.pressure
repl*i.pressure  repl*repl repl*repl*i.pressure

See -help fvvarlist- for more information

Scott


On Wed, Mar 13, 2013 at 8:55 PM, Sun, Wensheng <wsun@bcm.edu> wrote:
> Hi Scott,
>
> It works. By the way, could you explain what "i.pressure c.repl##c.repl##i.pressure" means?
>
> Thank you very much!
>
> Wensheng
>
> ________________________________________
> From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] On Behalf Of Scott Merryman [scott.merryman@gmail.com]
> Sent: Wednesday, March 13, 2013 8:09 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: marginsplot after xtmixed with square term
>
> Stata does not know that repl2 is the square of repl.
>
> Try:
>
>
> webuse acmemanuf
> lowess y repl, by(pressure)
> //gen repl2=repl^2
> gen id=.
> replace id=temp if pressure==1
> replace id=temp+3 if pressure==2
> replace pressure=0 if pressure==1
> replace pressure=1 if pressure==2
> xtmixed y  i.pressure c.repl##c.repl##i.pressure  || id: repl,
> cov(uns) res(ind) mle variance
> margins pressure, at(repl=(1(1)10))
> marginsplot
>
> Scott
>
>
> On Wed, Mar 13, 2013 at 12:43 PM, Sun, Wensheng <wsun@bcm.edu> wrote:
>> Please help! Marginsplot after xtmixed model contend square-term (wish to get concaved curves instead of straight lines).
>> webuse acmemanuf
>> lowess y repl, by(pressure)
>> gen repl2=repl^2
>> gen id=.
>> replace id=temp if pressure==1
>> replace id=temp+3 if pressure==2
>> replace pressure=0 if pressure==1
>> replace pressure=1 if pressure==2
>> xtmixed y c.repl## i.pressure c.repl2##i.pressure  || id: repl, cov(uns) res(ind) mle variance
>> margins pressure, at(repl=(1(1)10))
>> marginsplot
>>
>> I expected to get concaved curves from marginsplot like I usually got from modeling estimates with square terms; however, what I got here were two straight lines. Please help me to fix my codes.
>>
>> Thank you very much!
>>
>> Wensheng
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