Lets say that I predicted plant productivity (logy) by precipitation (logx1) and moisture content of soil (logx2). my original data gives me the best result only after taking logarithm on both side of variables.
mod <- lm(logy ~ poly(logx1*logx2, 2, raw=TRUE)
then I got following coefficients from the model:
intercept=6.773; logx1*logx2 poly(1) = 2.511; logx1*logx2 poly(2) = 0.458
With regard to equation, I have 2 questions: 1. How I can explain the result of this equation 2. How to find the value when precipitation is 0.
Thanks in advance!