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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 22:26:29 +0200

<> 

" I corrected the matrix to
replace marg=A[1,57] in `i'"

Just give me a hint why you did that...

You could simply pick one of the values of your varmain, and plug it into
-mfx, such as seen here for the value you mentioned earlier. Then list the
contents of the matrix with the marginal effects.


*************
mfx, var(varmain) at(varmain=42.6)
mat list e(Xmfx_dydx)
*************

and show us the output...


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 22:14
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: AW: why is this graph all over the place?

Replacing it with -levelsof- made it work! Thanks.
But I don't know why the marginal effects are not recorded. However, I
corrected the matrix to
replace marg=A[1,57] in `i'
Thanks in advance again,
Nirina
On Mon, Sep 21, 2009 at 4:05 PM, Martin Weiss <martin.weiss1@gmx.de> wrote:
>
> <>
>
> 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 -levelsof-, it is an out-of-date command, apparently with limited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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