[R] boot function returns the same results every time - there appears to be not resampling of the original data.

[John Sorkin]

R 2.8.1
windows XP

I am trying to learn how to use the boot function to perform a bootstrap of a regression. I have written a short trial program, shown below. Clearly I have done something wrong as the output of each of the 100 bootstrap values for the regression are exactly the same - there does not appear to be any bootstrap respampling!. What have I done wrong?


# Define function to be run. Function will return
# beta coefficeint for x.
fitter<-function(d)
{
  fit1<-lm(y~x,data=d)
  print(names(fit1))
  print(summary(fit1))
  summary(fit1)$coefficients[2,1]
}

# Define dataframe
x<-1:10
y<-x+rnorm(10)
d<-data.frame(x,y)


#Run boot strap
boot(d,fitter,R=100,sim="parametric")



John David Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
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