[R] logistic regression

[Mike Lawrence]

Maybe try making sure the data is numeric:

fac.to.num=function(x) as.numeric(as.character(x))


On 26-Jul-07, at 9:34 AM, Sullivan, Mary M wrote:

> Greetings,
>
>
> I am working on a logistic regression model in R and I am  
> struggling with the code, as it is a relatively new program for  
> me.  In searching Google for 'logistic regression diagnostics' I  
> came Elizabeth Brown's Lecture 14 from her Winter 2004  
> Biostatistics 515 course  (http://courses.washington.edu/b515/ 
> l14.pdf) .  I found most of the code to be very helpful, but I am  
> struggling with the lines on to calculate the observed and expected  
> values in the 10 groups created by the cut function.  I get error  
> messages in trying to create the E and O matrices:  R won't accept  
> assignment of "fi1c==j" and it won't calculate the sum.
>
>
>
> I am wondering whether someone might be able to offer me some  
> assistance...my search of the archives was not fruitful.
>
>
>
> Here is the code that I adapted from the lecture notes:
>
>
>
> fit <- fitted(glm.lyme)
>
> fitc <- cut(fit, br = c(0, quantile(fit, p = seq(.1, .9, .1)),1))
>
> t<-table(fitc)
>
> fitc <- cut(fit, br = c(0, quantile(fit, p = seq(.1, .9, .1)), 1),  
> labels = F)
>
> t<-table(fitc)
>
>
>
> #Calculate observed and expected values in ea group
>
> E <- matrix(0, nrow=10, ncol = 2)
>
> O <- matrix(0, nrow=10, ncol=2)
>
> for (j in 1:10) {
>
>       E[j, 2] = sum(fit[fitc==j])
>
>       E[j, 1] = sum((1- fit)[fitc==j])
>
>       O[j, 2] = sum(pcdata$lymdis[fitc==j])
>
>       O[j, 1] = sum((1-pcdata$lymdis)[fitc==j])
>
>
>
> }
>
>
>
> Here is the error message:  Error in Summary.factor(..., na.rm =  
> na.rm) :
>         sum not meaningful for factors
>
>
>
>
>
> I understand what it means; I just can't figure out how to get  
> around it or how to get the output printed in table form.  Thank  
> you in advance for any assistance.
>
>
>
> Mary Sullivan
>
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> and provide commented, minimal, self-contained, reproducible code.

--
Mike Lawrence
Graduate Student, Department of Psychology, Dalhousie University

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