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

[Xiaobo Gu]

>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 ?






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