[R] Adjusting two continuous variables by one continuous vari able

Liaw, Andy andy_liaw at merck.com
Tue Aug 3 20:18:36 CEST 2004

Graphically, you can use coplot() or lattice to see how the relationship
between height and weight changes with age.

With a linear model, you can do something like:

lm(height ~ weight * age, ...)

and work out the interpretation of the coefficients.


> From: Peter Tait
> Hi,
> I want to look at the relationship between 2 
> continuous/quantitative variables while adjusting for a third 
> continuous variable. For example: relationship between height 
> and weight adjusted for age.
> As I understand it using a glm would work if I had a 
> categorical variable (I could make age into a categories) but 
> I am interested to know if anyone knows how I can do this 
> analysis with out making age into categories.
> Any help would be appreciated.
> Cheers
> Peter

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