Oh, because When I did
mat list e(Xmfx_dydx)
I got:
e(Xmfx_dydx) [1, 57]
On Mon, Sep 21, 2009 at 4:26 PM, Martin Weiss <[email protected]> wrote:
>
> <>
>
> " 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: [email protected]
> [mailto:[email protected]] Im Auftrag von Nirina F
> Gesendet: Montag, 21. September 2009 22:14
> An: [email protected]
> 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 <[email protected]> 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 -levelsof-, it is an out-of-date command, apparently with limited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: [email protected]
>> [mailto:[email protected]] Im Auftrag von Nirina F
>> Gesendet: Montag, 21. September 2009 21:33
>> An: [email protected]
>> 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 <[email protected]>
> 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: [email protected]
>>> [mailto:[email protected]] Im Auftrag von Nirina F
>>> Gesendet: Donnerstag, 17. September 2009 18:46
>>> An: [email protected]
>>> 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 <[email protected]>
>> 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: [email protected]
>>>> [mailto:[email protected]] Im Auftrag von Nirina F
>>>> Gesendet: Donnerstag, 17. September 2009 17:55
>>>> An: [email protected]
>>>> 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 <[email protected]>
>>> 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: [email protected]
>>>>> [mailto:[email protected]] Im Auftrag von Nirina F
>>>>> Gesendet: Donnerstag, 17. September 2009 13:41
>>>>> An: [email protected]
>>>>> 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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