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AW: st: AW: why is this graph all over the place?


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   AW: st: AW: why is this graph all over the place?
Date   Fri, 18 Sep 2009 00:19:29 +0200

<> 

Try this and check it very carefully. I could not find such a picture in
Long and Freese (2006), http://www.stata-press.com/books/regmodcdvs.html, -
which I regard as a bad sign. 

Also note I am using the old -mfx- here, as I have not fully gotten my head
round the -margins- command. Hence the -version- statement...


*************
vers 10.1

qui{
	sysuse auto, clear
	prob for price mpg rep78 /*
	*/  headroom trunk weight
	
	ins mpg
	loc uniq= r(N_unique)
	
	su mpg, mean
	prgen mpg, from(`r(min)')  /*
	*/ to(`r(max)') /*
	*/ gen(prob) n(`uniq')
	
	
	levels mpg
	
	loc i 1
	gen marg=0
	
	foreach level in `r(levels)'{
		mfx, var(mpg) at(mpg=`level')
		mat A = e(Xmfx_dydx)
		replace marg=A[1,2] in `i'
		loc ++i
	}
	
}	

	tw (connected probp1 probx), /*
	*/ xti("Mpg") ytit("Probability") /* 
	*/ name(prob, replace) nodraw
	
	tw (connected marg probx), /*
	*/ xti("Mpg") ytit("Marginal Effect") /* 
	*/ name(marginal, replace) nodraw


gr combine prob marginal
*************



HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Nirina F
Gesendet: Donnerstag, 17. September 2009 18:46
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: AW: why is this graph all over the place?

Dear Martin,

Thank you very much for the clarification.
How about graphing the marginal effects next to that graph?
nrina

On Thu, Sep 17, 2009 at 12:04 PM, Martin Weiss <martin.weiss1@gmx.de> wrote:
>
> <>
>
> The -prgen- command holds all other covariates at their mean by default,
so
> my code has already taken care of your concern. To change the -title-s:
>
> *************
> sysuse auto, clear
> prob for price mpg rep78 /*
> */  headroom trunk weight
>
> ins mpg
> loc uniq= r(N_unique)
>
> su mpg, mean
> prgen mpg, from(`r(min)')  /*
> */ to(`r(max)') /*
> */ gen(prob) n(`uniq')
>
> tw (connected probp1 probx), /*
> */ xti("Mpg") ytit("Probability")
> *************
>
>
>
> HTH
> Martin
>
>
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Nirina F
> Gesendet: Donnerstag, 17. September 2009 17:55
> An: statalist@hsphsun2.harvard.edu
> Betreff: Re: st: AW: why is this graph all over the place?
>
> Thank you very much Martin for  your help. It worked so well.
>
> I have a few questions:
>
> is it possible also to graph the marginal effects of just the mpg at
> each value of mpg. I know if you calculate
> . mfx
> after
> . prob for price mpg rep78 headroom trunk weight
>
> then you get the marg. effects at the mean value but I would like the
> marginal effects at each value of mpg but keeping the other variables
> at their mean. I am aware of the -at- option but it's just difficult
> to graph it.
>
> Also, How would I change the name of the xaxis and yaxis of the previous
> graph?
>
> Thank you very much,
>
> Nrina
>
>
> On Thu, Sep 17, 2009 at 8:00 AM, Martin Weiss <martin.weiss1@gmx.de>
wrote:
>>
>> <>
>>
>> For these purposes, Scott Long`s -findit spost- comes in handy. Of
course,
>> Long and Freese (2006), http://www.stata-press.com/books/regmodcdvs.html,
> is
>> the canonical reference for what you are trying to achieve. Try this:
>>
>>
>> *************
>> sysuse auto, clear
>> prob for price mpg rep78 /*
>> */  headroom trunk weight
>>
>> ins mpg
>> loc uniq= r(N_unique)
>>
>> su mpg, mean
>> prgen mpg, from(`r(min)')  /*
>> */ to(`r(max)') /*
>> */ gen(prob) n(`uniq')
>>
>> tw (connected probp1 probx)
>> *************
>>
>>
>>
>> HTH
>> Martin
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: owner-statalist@hsphsun2.harvard.edu
>> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Nirina F
>> Gesendet: Donnerstag, 17. September 2009 13:41
>> An: statalist@hsphsun2.harvard.edu
>> Betreff: st: why is this graph all over the place?
>>
>> Dear all,
>>
>> I would like to graph the predicted probabilities of  having foreign
>> against mpg in order to highlight the slope(basically the marginal
>> effects) at each value of mpg.
>> I run the following but it is all over the place because I think it is
>> giving me the predicted probabilities from different variables.
>> Could you help me in this please. also if you could help me graph the
>> marginal effects of mpg from this probit equation against each value
>> of mpg.
>>
>> probit  foreign price mpg rep78 headroom trunk weight
>> predict pmpg, p
>> sort mpg
>> twoway line  pmpg mpg
>>
>> Thank you veyr much,
>> N
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