the length of bar for Gabriel's barplot

Show the upper or lower confidence interval of Gabriel's barplot.

Usage

rgabriel(x, f, a = 0.05)

Arguments

x: data vector
f: factor vector
a: alpha level of mutiple comparison.

Value

vstar: the length of the bar for mutiple comparision

Details

As shown in Gabriel's paper,use M(alpha,k*,v), the upper alpha point of the Studentized Maximum Modulus of k* normals and v df. And this method is a graphical way for visually mutiple comparision.

References

Gabriel, K.R., 1978. A Simple Method of Multiple Comparisons of Means. Journal of the American Statistical Association 73, 724.

Stoline, M.R., Ury, H.K., 1979. Tables of the Studentized Maximum Modulus Distribution and an Application to Multiple Comparisons among Means. Technometrics 21, 87.

Author

Yihui XIE

Miao YU

Examples


# equal numbers

g <- c(1:50)
f <- c(rep(1,10),rep(2,10),rep(3,10),rep(4,10),rep(5,10))
gabriel.plot(g,f,rgabriel(g,f))


# unequal numbers

g <- c(1:40)
f <- c(rep(1,3),rep(2,12),rep(3,15),rep(4,5),rep(5,5))
gabriel.plot(g,f,rgabriel(g,f))