Hi,

I've an issue adding an interaction to a GAMM:

My model was of form:

gamm1 <- gamm(TOTSR ~ fROT + s(PH) + s(LOI) + s(ASP) + s(SQRT_ELEV) + CANCOV
+ s(SQRT_TOTCWD) + s(WELLF) + s(WELLN) + s(OLDWDLD) + s(DISTWOOD) +
s(Annprec) + s(OLDWDLD:DISTWOOD) + (1|fSITE),  family = poisson, data =
BIOFOR2)

with interaction of s(OLDWDLD:DISTWOOD).

However I got this error message below but don't know what it means? (my
data is composed of info for 150 plots)

#I Warning messages:
#2: In OLDWDLD:DISTWOOD :
 # numerical expression has 150 elements: only the first used
#3: In OLDWDLD:DISTWOOD :
#  numerical expression has 150 elements: only the first used

Can anyone offer advice on how to include this interaction in GAMM model?
Thanks

Karen Moore

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