[R] model formula
Bill Simpson
William.Simpson at drdcrddc.gc.ca
Tue Nov 18 14:40:36 CET 2003
I have continuous variables x, y, z. The plot of the data looks like this:
y
 z=1(o), 2(@), 3(#), 4(*)

* * *


# # # #


@ @ @ @

 o
 o
 o
 o
o
 x
The correct model appears to be: if z==1, y~x+z; else y~z
(y~z + z:x isn't it)
How can I express this model in lm()? If I can't express it properly in
lm(), what is the best way to fit the model?
Thanks for any help.
Bill Simpson
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