Re: st: problem with Margin command and interaction graph in fixed effect logistic regression

[Nahla Betelmal <nahlaib@gmail.com>]

Thank you both Alfonso and Klaus for the great help.

I run the following command for each interaction, all worked fine.

margins DV, predict(pu0) at( IVA=(-1.5(0.5)1.5))

margins DV, predict(pu0) at( IVB=(-1.5(0.5)1.5))

margins DV, predict(pu0) at( IVC=(-1.5(0.5)1.5))

I did not use dydx as I did not fully understand it

Thank you so much

Nahla

On 31 October 2013 18:57, Alfonso Sánchez-Peñalver
<alfonso.statalist@gmail.com> wrote:
> Hi Nahla,
>
> I’ve digged a little more into this. First, I found this in the archive using clogit and margins:
>
> http://www.stata.com/statalist/archive/2010-08/msg01454.html
>
> It seem that you have to specify the dydx() and predict options to have it work. To illustrate, the following two examples work
>
> ——————————— Begin Code ——————————————
> webuse lowbirth2, clear
> clogit low lwt smoke ptd ht ui i.race, group(pairid)
> margins race, dydx(lwt) predict(pu0) at(lwt=(100(10)200))
> ——————————— End Code ———————————————
>
> However, the following does not
>
> ——————————— Begin Code ——————————————
> webuse lowbirth2, clear
> clogit low c.lwt##i.smoke ptd ht ui i.race, group(pairid)
> margins race, dydx(lwt) predict(pu0) at(lwt=(100(10)200))
> ——————————— End Code ———————————————
>
> The problem is that it predicts the marginal effects when the fixed effects are zero. I hope this sheds some light.
>
> Alfonso
>
> On Oct 31, 2013, at 12:51 PM, Nahla Betelmal <nahlaib@gmail.com> wrote:
>
>>> margins drug, at(studytime=(10(5)30))
>
>
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