R-users
E-mail: r-help@r-project.org

   Hi! R-users.

   A simple object as below was created to see how gam() of
package "mgcv" and anova() work.

function()
{
  library(mgcv)
  set.seed(12)
  nd <- 100
  xx1 <- runif(nd, min=1, max=10)
  xx1 <- sort(xx1)
  yy <- sin(xx1)+rnorm(nd, mean=5, sd=5)
  data1 <- data.frame(x1=xx1, y=yy)
  fit1 <- gam(y~s(x1, k=5), data=data1, family=gaussian)
  out1 <- anova(fit1)
  print(out1)
}

The results is:

Family: gaussian
Link function: identity
Formula:
y ~ s(x1, k = 5)
Approximate significance of smooth terms:
        edf Ref.df     F p-value
s(x1) 3.367  3.867 1.992   0.104

   I do not understand why the value of "Ref.df" is larger than "edf"
by 0.5. And I failed to find out an equation to derive the F value(1.992).
Any help would be greatly appreciated.

*****    r.otasuke@gmail.com    *****

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