The easiest work-around I've found for this problem is to create a vector in
your data frame just using numbers to order them how you want, create a
separate "labeling" data frame with those numbers and corresponding text
labels, and then enter the vector with the grouping names from the labeling
frame in boxplot's 'names' argument. As such:
dir <- "D:\\"
setwd(dir)
data <- read.csv("ODR.csv")
type <- read.csv("soil_type.csv")
boxplot(data=data, Sat..ODR~Type_num, *names=type$Soil.type*, col="light
green", main="ODR by soil type", xlab="Soil type", ylab="ODR")
The labeling data frame should look something like this: