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Re: st: Marginsplot after Poisson regression and negative predicted values


From   James Bernard <[email protected]>
To   [email protected]
Subject   Re: st: Marginsplot after Poisson regression and negative predicted values
Date   Wed, 8 Jan 2014 22:19:10 +0800

The model is like this

-xtpoisson y x1 x2 x3

y is the count variable

-margins, at(x1=(0(1)20))

-marginsplot, noci

On Wed, Jan 8, 2014 at 10:11 PM, Maarten Buis <[email protected]> wrote:
> What are the exact commands you used? The defaults should not result
> in negative predicted counts.
>
> -- Maarten
>
> On Wed, Jan 8, 2014 at 2:52 PM, James Bernard <[email protected]> wrote:
>> Forgot to add that I am not interested in confidence interval. My
>> dependent variable has maximum of 300. However, the maximum of y axis
>> on the predicted plot is 1
>>
>> On Wed, Jan 8, 2014 at 9:47 PM, James Bernard <[email protected]> wrote:
>>> No, I mean that the Y variable that is a count variable on the y axis
>>> is negative, while my dependent variable is  count variable
>>>
>>> On Wed, Jan 8, 2014 at 5:37 PM, Maarten Buis <[email protected]> wrote:
>>>> I suspect that you mean the confidence interval around the predicted
>>>> values. It is a known issue with the delta method that is used by
>>>> -margins- for computing the confidence interval. Generally I would not
>>>> worry too much about it, as these bounds are failry approximate
>>>> anyhow, but if you do you can predict the linear predictor with its
>>>> confidence intervals and transform those to the expected count metric
>>>> as in <http://www.stata.com/support/faqs/statistics/delta-rule/index.html>.
>>>>
>>>> Hope this helps,
>>>> Maarten
>>>>
>>>>
>>>> On Wed, Jan 8, 2014 at 9:51 AM, James Bernard <[email protected]> wrote:
>>>>> Hi all,
>>>>>
>>>>> I have ran a Poisson model. Then tried to run -margins and
>>>>> -marginsplot for one of the variables.
>>>>>
>>>>> The shape of the graph makes sense. But, the range of predicted values
>>>>> of the dependent variable (which is a count variable, obviously)
>>>>> ranges from 1 at its maximum and -6 at its minimum. Is this usual? Am
>>>>> I doing something wrong?
>>>>>
>>>>> Thanks,
>>>>> James
>>>>> *
>>>>> *   For searches and help try:
>>>>> *   http://www.stata.com/help.cgi?search
>>>>> *   http://www.stata.com/support/faqs/resources/statalist-faq/
>>>>> *   http://www.ats.ucla.edu/stat/stata/
>>>>
>>>>
>>>>
>>>> --
>>>> ---------------------------------
>>>> Maarten L. Buis
>>>> WZB
>>>> Reichpietschufer 50
>>>> 10785 Berlin
>>>> Germany
>>>>
>>>> http://www.maartenbuis.nl
>>>> ---------------------------------
>>>> *
>>>> *   For searches and help try:
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>>>> *   http://www.ats.ucla.edu/stat/stata/
>> *
>> *   For searches and help try:
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>> *   http://www.ats.ucla.edu/stat/stata/
>
>
>
> --
> ---------------------------------
> Maarten L. Buis
> WZB
> Reichpietschufer 50
> 10785 Berlin
> Germany
>
> http://www.maartenbuis.nl
> ---------------------------------
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/faqs/resources/statalist-faq/
> *   http://www.ats.ucla.edu/stat/stata/
*
*   For searches and help try:
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