Nothing
sen.adichie<-function (z, example=F, r=3)
{
# This code tests for parallel lines.
# Based on chapter 9 of:
#
# Nonparametric Statistical Methods, 3e
# Hollander, Wolfe & Chicken
#
# z is a list of paired vectors. Each item in the list is a set
# of two paired vectors in the form of a matrix. The first column
# of each matrix is the x vector, the second in the y vector.
#
# Inefficiently programmed by Eric Chicken, October 2012.
if(example)
{
# Example 9.5 data
x1 <- x2 <- x3 <- x4 <- c(0, 1.5, 3, 4.5, 6)
y1 <- c(0, 33.019, 111.314, 196.205, 230.658)
y2 <- c(0, 131.831, 181.603, 230.07, 258.119)
y3 <- c(0, 33.351, 97.463, 196.615, 217.308)
y4 <- c(0, 8.959, 105.384, 211.392, 255.105)
z <- list(cbind(x1, y1), cbind(x2, y2), cbind(x3, y3),
cbind(x4, y4))
}
k <- length(z)
x.bar <- beta.bar.num <- beta.bar.den <- numeric(0)
for(i in 1:k)
{
# (9.41)
x.bar <- c(x.bar, mean(z[[i]][,1]))
# (9.40)
beta.bar.num <- c(beta.bar.num,
sum((z[[i]][, 1] - x.bar[i]) * z[[i]][, 2]))
beta.bar.den <- c(beta.bar.den,
sum((z[[i]][, 1] - x.bar[i])^2))
}
beta.bar <- sum(beta.bar.num) / sum(beta.bar.den)
# (9.42) - (9.45)
V <- numeric(0)
for(i in 1:k)
{
z[[i]][, 2] <- z[[i]][, 2] - beta.bar * z[[i]][, 1]
T.i <- (z[[i]][, 1] - x.bar[i]) * rank(z[[i]][, 2])
T.i <- sum(T.i) / (length(z[[i]][, 1]) + 1)
V <- c(V, T.i^2 / beta.bar.den[i])
}
V <- 12 * sum(V)
p <- pchisq(V, df=(k - 1), lower.tail=F)
cat("\n")
cat("Null: all slopes are equal")
cat("\n")
cat(paste("V = ", round(V, r), ", P = ", round(p, r), sep=""))
cat("\n")
}
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