Hi Melissa,

I would highly encourage you to read [1].  It would be extremely beneficial
for your understanding of the type of models you should use in a situation
like yours (count data).

Best regards,
Jorge.-

[1]  cran.r-project.org/web/packages/pscl/vignettes/countreg.pdf



On Wed, Apr 4, 2012 at 1:10 AM, Melrose2012 <> wrote:

> Thank you for your reply.
>
> I do understand that I am working in log space with the default link
> function of the binomial being "logit."  My problem is, I thought that they
> way I had written the code, when I did the "lines" command, it should plot
> the best-fit line (found by 'glm') on top of my graph.  As you can see,
> however, this clearly did not work and I am off by several factors of
> magnitude.  I am not sure if the problem lies in the way I have done the
> 'glm' or in the plotting.
>
> If I understand the function correctly, when I do 'glm' of family=binomial,
> I am working in log space (hence the link function default being "logit.")
> If this is correct, then doesn't either my data have to be converted to log
> space also or the results of my 'glm.fit' be converted to linear space
> (i.e.
> using 'inv.logit' from the boot library)?  This was my thought process
> behind plotting the data as log (I tried several other obviously useless
> iterations of various scalings.)  It appears that you can not do an
> inv.logit on the result from the 'glm' command.
>
> If I try to do this:   inv.logit(glm.fit)
> I get an error saying:  Error in plogis(q, location, scale, lower.tail,
> log.p) : Non-numeric argument to mathematical function
>
> I'm pretty sure this is a limitation in my understanding of exactly what R
> is doing in this logistic regression and I am having a hard time finding
> help online or in the R help files that helps me to decipher this problem.
>
> Can anyone tell me if I have set up the 'glm' wrong or if the error is in
> how I am trying to plot the best-fit line on the data?
>
> I am new to these sorts of statistics and data manipulation, so I
> acknowledge my ignorance and appreciate whatever help anyone can give me.
>
> Thank you again!
>
> Cheers,
> Melissa
>
> --
> View this message in context:
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> Sent from the R help mailing list archive at Nabble.com.
>
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