[R] What does the : operator mean in glm formulas

[David Winsemius]

On Jan 19, 2012, at 8:56 AM, Xiaobo Gu wrote:

>> Such a model consists of a series of terms separated by +operators.
> In the above ,term means individual variable.
>
>> The terms themselves consist of variable and factor names separated  
>> by : operators.
> What does term mean in this?
>
>> Such a term is interpreted as the interaction of all the variables  
>> and factors appearing in the term.
>
> What does interaction mean, and what does term mean here ?
>

I'm sorry. This is the wrong list to request tutoring in basic  
statistics. If you don't know what an interaction is, it suggests that  
you do not have sufficient education to safely use R or any other  
statistics package for that matter. You should go back to any basic  
regression textbook (or perhaps do a web-search) and do sufficient  
self-study to answer that question.

-- 
David.


> Xiaobo Gu
>
> From: David Winsemius
> Date: 2012-01-19 21:46
> To: guxiaobo1982
> CC: r-help; ds5j
> Subject: Re: [R] What does the : operator mean in glm formulas
>
> On Jan 19, 2012, at 8:02 AM, Xiaobo Gu wrote:
>
>> Hi,
>>
>> I see the following is the credit scoreing in R guide :
>>
>> m2<-glm(formula = good_bad ~ checking + duration + history+ purpose
>> +amount + savings + employed + installp + marital +
>> coapp +age + other + depends + telephon + foreign +checking:amount
>>
>> What does checking:amount mean?
>
> ?formula
>
> -- 
>
> David Winsemius, MD
> West Hartford, CT

David Winsemius, MD
West Hartford, CT