[R] Inverse Gaussian Distribution

David Winsemius dwinsemius at comcast.net
Tue Jan 4 14:52:46 CET 2011

On Jan 4, 2011, at 7:50 AM, Louisa wrote:

> Thank you!
> But i'm wondering:
> if you run
> area <- factor(area, levels=c("C", "A","B","D","E","F") )
> then you are transforming only 'area',  aren't you?
> isn't it possible to transform the whole data like i did for agecat
> but now for area and area C as baseline,

Of course, but may I point out that you did no earlier say that you  
may have attached a dataframe containing "area". There are many  
confusing situations that arise when using attached dataframes and  
this may be one of them. Many experienced R users avoid attaching data  
objects like the plague.

> or are you doing so when you run
>> area <- factor(area, levels=c("C", "A","B","D","E","F") )
>> attach(data)
> and then run the model with area as predictorvariable:
>> model <- glm(Y~ agecat+gender+area,...)

> My question is if i can run it as follows and still have a right  
> solution :
>> data <-transform(data, area=(factor(area, levels=c("C",
>> "A","B","D","E","F") ) )

Is there any reason that you suspect this will not work? Why not try  
it ... now assumimg that you failed to tell us that area was a column  
in a dataframe that is. (One set of parentheses appear extraneous.)

data <-transform(data, area = factor(area, levels=c("C",  
"A","B","D","E","F") )

(Untested in the absence of reproducible example ,,, but it looks as  
though it might work.)

> I'll be very grateful for any help you can provide!
> Kind regards,
> Louisa
> -- 
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David Winsemius, MD
West Hartford, CT

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