I have developed a GAM model in order to predict Y using 4 X variables. 2 of these X's are factors, and 1 is a spline.
Part of the data looks like: Days WRM variety PWM O_EC 31 75 1 90 234 31 79 1 78 283 31 82 1 92 281 31 84 1 96 213 31 99 2 69 247 31 100 2 77 324 31 104 2 74 259 31 118 2 81 282 31 61 3 58 478 31 98 3 83 429 31 98 3 70 379 31 156 3 87 467 31 78 4 56 283 31 97 4 67 282 31 106 4 69 368 31 184 4 78 386 39 66 1 204 233 39 83 1 265 360 39 87 1 270 308 39 236 1 243 323 39 174 2 244 300 39 181 2 257 366 39 241 2 305 408 39 282 2 299 599 39 125 3 153 402 39 156 3 213 384 39 183 3 227 408 39 217 3 235 360 39 159 4 205 362 39 180 4 182 314 39 189 4 224 488 39 246 4 265 468 fdays = factor(Days) fvar = factor(variety) my model is: test1 <- gam(O_EC~s(WRM)+PWM+fdays+fvar) Now, I can easily measure O_EC, PWM, fvar, and fdays, but not WRM. I can get a good estimate for s(WRM) by straight algebra and get a rough eyeball estimate of WRM from the s(WRM) vs WRM plot: s(WRM) ~ O_EC - B0 - B1*PWM - B2*fdays - B3*fvar Is there any way of using a backSpline or other inverse spline since s(WRM) is not monotone? Or is it possible to obtain a formula for the smooth that I can mathematically solve for? Thank you, Geoff -- Be Yourself @ mail.com! Choose From 200+ Email Addresses Get a Free Account at www.mail.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
