Re: [R] Why there is no p-value from likelihood ratio test using anova in GAM model fitting?

2009-04-28 Thread Ben Bolker
willow1980 wrote: Hi, Dieter, I did add (test=F) in my script, but it does not matter. The following is my whole script. # modelsurs_fer13-gam(sum_surv15~s(FLBS)+SES+s(byear)+s(FLBS,byear),family=quasipoisson)

Re: [R] Why there is no p-value from likelihood ratio test using anova in GAM model fitting?

2009-04-28 Thread willow1980
Hi, Dieter, I did add (test=F) in my script, but it does not matter. The following is my whole script. # modelsurs_fer13-gam(sum_surv15~s(FLBS)+SES+s(byear)+s(FLBS,byear),family=quasipoisson)

Re: [R] Why there is no p-value from likelihood ratio test using anova in GAM model fitting?

2009-04-28 Thread willow1980
Hi, Simon, I am using mgcv:gam and the version number is mgcv_1.5-2. I also exchanged the order of two models in anova, but this also did not help. From the differences in DF(0.77246) and deviance (-0.02), these two models seem to be not significantly different. Isn't it? Thank you anyway!

Re: [R] Why there is no p-value from likelihood ratio test using anova in GAM model fitting?

2009-04-28 Thread Simon Wood
The issue isn't really about which order you supply the models to `anova'. The problem is that there is no meaningful test to perform with these two models, because the `larger' model has actually been estimated as having a *larger* deviance than the `smaller' model, so there is never going

[R] Why there is no p-value from likelihood ratio test using anova in GAM model fitting?

2009-04-28 Thread willow1980
Hello, everybody, There is the first time for me to post a question, because I really cannot find answer from books, websites or my colleagues. Thank you in advance for your help! I am running likelihood ratio test to find if the simpler model is not significant from more complicated model.

Re: [R] Why there is no p-value from likelihood ratio test using anova in GAM model fitting?

2009-04-28 Thread Dieter Menne
willow1980 jianghua.liu at shef.ac.uk writes: However, when I run LRT to compare them, the test did not return F value and p-value for me. What's the reason? Analysis of Deviance Table Model 1: sum_surv15 ~ s(FLBS) + s(byear) + s(FLBS,

Re: [R] Why there is no p-value from likelihood ratio test using anova in GAM model fitting?

2009-04-28 Thread Simon Wood
The simpler model has the lower deviance (marginally), so there is nothing to test here. This can happen with maximum penalized likelihood estimators, even though the models are nested (especially if the smoothing parameters are selected automatically). Are you using gam:gam or mgcv:gam (and