如何对 R 中元素包含数字和字母的字符向量进行排序？

Question

My character array is the following: Note: the array was changed. Sorry, my mistake

m <- c("VI-2005","III-2005","II-2005","I-2005","III-2006","II-2006","I-2006","VI-2006","IV-2007","III-2007","II-2007","I-2007")

I have roman numbers and years. I would like to sort it in descending order so that I will have an output like this:

I-2005
II-2005
III-2005
IV-2005
I-2006
II-2006
III-2006
IV-2006
I-2007
II-2007
III-2007
IV-2007

I had try the mixedsort from the "gtools" package:

> # install.packages("gtools") ## Uncomment if not already installed
> library(gtools)
> mixedsort(m)

But it doesn't sort by the roman numbers. Thank you for reading!

Answer 1

Split the input and transform the roman numerals into a factor:

library(data.table)
n <- tstrsplit(m, "-")
n[[1]] <- ordered(n[[1]], levels = c("I", "II", "III", "IV", 
                                    "V", "VI", "VII", "VIII", 
                                    "IX", "X", "XI", "XII"))
n[[2]] <- as.integer(n[[2]])
n <- rev(n)

m[do.call(order, n)]
#[1] "I-2005"   "I-2005"   "II-2005"  "III-2005" "VI-2005"  "VI-2005"  "II-2006"  "III-2006"
#[9] "I-2007"   "II-2007"  "III-2007" "IV-2007" 

Edit:

If you want to use this for plotting or modelling, turn m into an ordered factor:

library(data.table)
n <- tstrsplit(unique(m), "-")
n[[1]] <- ordered(n[[1]], levels = c("I", "II", "III", "IV", 
                                    "V", "VI", "VII", "VIII", 
                                    "IX", "X", "XI", "XII"))
n[[2]] <- as.integer(n[[2]])
n <- rev(n)    

m <- ordered(m, levels = unique(m)[do.call(order, n)])

Answer 2

You can use as.roman to convert roman numerals to their type and then use order to order the dataframe.

data <- strcapture('(\\w+)-(\\d+)', m, 
                   proto = list(roman = character(), number = numeric()))
data$roman <- as.roman(data$roman)
data <- data[do.call(order, rev(data)), ]

#   roman number
#4      I   2005
#7      I   2005
#3     II   2005
#2    III   2005
#1     VI   2005
#8     VI   2005
#6     II   2006
#5    III   2006
#12     I   2007
#11    II   2007
#10   III   2007
#9     IV   2007

If you want the string back, you can paste it:

do.call(paste, c(data, sep = '-'))
# [1] "I-2005"   "I-2005"   "II-2005"  "III-2005" "VI-2005"  "VI-2005"  "II-2006" 
# [8] "III-2006" "I-2007"   "II-2007"  "III-2007" "IV-2007" 

Answer 3

You could also use the as.roman function. This will ensure a number 6 ie VI is before 9 ie IX when sorting

s <- read.table(text=m, sep="-")
with(s, do.call(paste, c(sep="-", s[order(V2, as.roman(V1)), ])))

 [1] "I-2005"   "I-2005"   "II-2005"  "III-2005" "VI-2005"  "VI-2005"  "II-2006"  "III-2006"
 [9] "I-2007"   "II-2007"  "III-2007" "IV-2007"