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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   Mon, 21 Sep 2009 22:05:35 +0200

<> 

See, just when I thought I knew Stata: -levels- is not the abbreviation for
-levelsof-, it is an out-of-date command, apparently with limited
functionality. I never noticed, but you did with your non-integer value...
So replace it by -levelsof- and it should work:


*************
clear*
inp x
1
3
4.5
4
end
levelsof x
levels x
*************



HTH
Martin

-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Nirina F
Gesendet: Montag, 21. September 2009 21:33
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: AW: why is this graph all over the place?

Thank you very much Martin.
I tried the example and it worked perfectly. When I tried with my
variables, the one that replaces mpg has one value that  is not an
integer but is 42.6, therefore I got an error message:
levels varmain
varmain contains non-integer values
r(459);
I guess I should change the command -levels- with another one that
could list the values of varmain.
Also, I tried to recode varmain (42.6=43) but then I don't get
anything inside the new variable marg that keeps the marginal effects.
I am sure something is not right there  because your example works
perfectly. I am going through each  line to check.

Nirina

On Thu, Sep 17, 2009 at 6:19 PM, Martin Weiss <martin.weiss1@gmx.de> wrote:
>
> <>
>
> 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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>>
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