Question about GAMs
On Oct 13, 2011, at 11:20 AM, pigpigmeow wrote:
I'm confused... I type .. predict.gam(ozonea,type=s(ratio,bs="cr")) pressure maxtemp s(avetemp) s(ratio) 1 -0.0459102290 -0.185178463 0.263358446 -0.164558673 2 -0.0286464652 -0.194731320 0.199315027 0.727823293 3 0.0478073459 -0.013227033 0.002228896 0.342373202 4 -0.0089164494 0.082301539 -0.037331159 -0.067260889 5 0.0675373617 0.024984396 -0.047067786 -0.357569389 6 0.0823348735 0.101407254 -0.075884852 -1.485036738 7 -0.0977015204 0.177830112 -0.094755158 0.236575309 8 -0.0903027645 0.225594398 -0.113346667 0.435141242 9 0.0206785742 0.187382969 -0.066346157 -0.256133513 10 -0.1371615520 0.101407254 -0.131656887 0.145057584 11 -0.0477674066 -0.181001505 0.260279546 0.180513043 12 -0.0921599421 -0.009050075 -0.020511366 0.281470433 13 0.0681464361 -0.219212934 0.335348247 0.270813178 ...... I want to show s(ratio,bs="cr") term, and show the warning message Warning message: In predict.gam(ozonea, type = s(ratio, bs = "cr")) : Unknown type, reset to terms. I don't understand what does it mean. By the way, i use log-link function, should I convert log-link function of newozone to fitted value of newozone? 1. log(newozone) - s(ratio,bs="cr") = x then exp(x)
Perhaps. I do not see 'newozone' defined anywhere above and can only speculateo speculate. I'm pretty sure Wood's uncopied comment was intended to remind you that differences in the log (regression) scale are equivalent to ratios on the measured scales. So either : exp( diff(coef, log(measured_or_external_baseline) ) ) # OR exp(coef)/measured_or_external_baseline How that is properly calculated in pkg:mgcv is a separate issue and Simpson has suggested you read the help pages more carefully.
2. exp(newozone) - s(ratio,bs="cr") =X then x
Probably incorrect.
which one is correct? so confused
David Winsemius, MD West Hartford, CT