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From |
Partho Sarkar <partho.ss+lists@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Regression Equation in ZINB regression |

Date |
Tue, 20 Sep 2011 22:02:14 +0530 |

Rachel You are very welcome- and even I got to learn something new through this! Incidentally, I notice now some typos in my messages, but I think from the references I gave you will get a clear enough idea of how to interprete(emphasis) your results- and I would imagine that is what would be expected from a dissertation in biology. Best Partho On Tue, Sep 20, 2011 at 9:30 PM, rachel grant <rachelannegrant@gmail.com> wrote: > Thanks Partho for taking the time to help me. > It is becoming clearer. I am going to look into it further and I'll > come back to the list if I need more help > thanks again > Rachel > > On 20 September 2011 12:50, Partho Sarkar <partho.ss+lists@gmail.com> wrote: >> Oops, sorry again! My apologies- I am doing this in between other >> work. I meant to write: >> >> E[yi|xi]=count for x=xi =lambda[i]=a0+a1xi + etc, i.e., the >> probability lambda is different for different levels of xi. >> >> and >> >> L(y1,y2,..,yn)=F(lambda[1],lambda[2],...,lambda[n])=G(x1,x2,...,xn) >> >> Partho >> >> >> On Tue, Sep 20, 2011 at 5:09 PM, Partho Sarkar >> <partho.ss+lists@gmail.com> wrote: >>> Rachel, it seems you posted the same question under 2 headers- I just >>> replied on the thread: Regression Equation for Zero inflated negative >>> binomial. I wanted to make a slight correction- I said the parameter >>> lambda is is the LHS in the regression, which is not quite correct. >>> The mean (or expected) count is equal to lambda. So we really use the >>> fact that : >>> >>> E[yi|xi]=count for x=xi =lambda=a0+a1xi + etc. >>> >>> to get the "likelihood" of observing all the yi's as a function of the >>> observed xi's: >>> >>> L(y1,y2,..,yn)=F(lambda)=G(x1,x2,...,xn) >>> >>> and then maximize this likelihood function to estimate lambda. >>> >>> Hope this helps >>> >>> Partho >>> >>> On Tue, Sep 20, 2011 at 4:19 PM, Partho Sarkar >>> <partho.ss+lists@gmail.com> wrote: >>>> My post crossed yours in the mail! Hope you can manage now. >>>> >>>> Partho >>>> >>>> On Tue, Sep 20, 2011 at 4:03 PM, rachel grant <rachelannegrant@gmail.com> wrote: >>>>> Thank you Partho. Thank you all for your patience. >>>>> I have now understood that I cannot get Stata to do this and I need to >>>>> reconstruct by inserting my co-efficients into the equation. Fine >>>>> >>>>> Now the problem I have is finding a general equation for ZINB in order >>>>> to reconstruct. >>>>> Is the general equation for ZINB the same as Poisson? I cannot find >>>>> anywhere a general equation for ZINB. >>>>> I could use a general log-linear Poisson type equation but would this >>>>> be correct? and how do I deal with the inflated part, is this merely a >>>>> seperate log-linear eqn, or is it incorporated into th general ZINB >>>>> eqn. Thanks, Rachel >>>>> >>>>> On 19 September 2011 08:13, Partho Sarkar <partho.ss+lists@gmail.com> wrote: >>>>>> Hi Rachel >>>>>> >>>>>> Just to clarify: in order to actually get the "regression equation", >>>>>> by which I assume you mean something like >>>>>> >>>>>> yhat=12.56+2.6*x1+0.34*x2 , >>>>>> >>>>>> you do need to reconstruct the equation form the output displayed (as >>>>>> exemplified by Anees's results). You could see this page for an >>>>>> example: http://dss.princeton.edu/online_help/analysis/interpreting_regression.htm >>>>>> . >>>>>> >>>>>> With a little more programming effort, this process could be automated >>>>>> using e-class macros etc. (There is very probably a user-written >>>>>> program to do this somewhere out there- -estadd- from here >>>>>> http://repec.org/bocode/e/estout/ might help partly, and you can >>>>>> search the rich REPEC archives). >>>>>> >>>>>> (In this sense Stata may not be as "user friendly" as Minitab or even >>>>>> some more ambitious other packages, which helpfully report the exact >>>>>> "prediction equation" in the form you might want, but then it can do >>>>>> so much more besides!) >>>>>> >>>>>> Hope this helps >>>>>> >>>>>> Partho >>>>>> >>>>>>> On Mon, Sep 19, 2011 at 12:34 AM, rachel grant <rachelannegrant@gmail.com> wrote: >>>>>>>> >>>>>>>> I have searched the help files but I cannot understand how to get >>>>>>>> Stata to display the regression equation. >>>>>>>> If anyone is able to help, without referring me to manual, it would be >>>>>>>> really appreciated. >>>>>>>> >>>>>>>> -- >>>>>>>> regards, Rachel Grant >>>>>>>> * >>>>>>>> * For searches and help try: >>>>>>>> * http://www.stata.com/help.cgi?search >>>>>>>> * http://www.stata.com/support/statalist/faq >>>>>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>>>> >>>>>> >>>>>> * >>>>>> * For searches and help try: >>>>>> * http://www.stata.com/help.cgi?search >>>>>> * http://www.stata.com/support/statalist/faq >>>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> regards, Rachel >>>>> >>>>> * >>>>> * For searches and help try: >>>>> * http://www.stata.com/help.cgi?search >>>>> * http://www.stata.com/support/statalist/faq >>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>> >>>> >>> >> >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/statalist/faq >> * http://www.ats.ucla.edu/stat/stata/ >> > > > > -- > regards, Rachel > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**Re: st: Regression Equation in ZINB regression***From:*rachel grant <rachelannegrant@gmail.com>

**Re: st: Regression Equation in ZINB regression***From:*Partho Sarkar <partho.ss+lists@gmail.com>

**Re: st: Regression Equation in ZINB regression***From:*rachel grant <rachelannegrant@gmail.com>

**Re: st: Regression Equation in ZINB regression***From:*Partho Sarkar <partho.ss+lists@gmail.com>

**Re: st: Regression Equation in ZINB regression***From:*Partho Sarkar <partho.ss+lists@gmail.com>

**Re: st: Regression Equation in ZINB regression***From:*Partho Sarkar <partho.ss+lists@gmail.com>

**Re: st: Regression Equation in ZINB regression***From:*rachel grant <rachelannegrant@gmail.com>

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