In python, I can do something like
a = [1,100,5,-5,-7,99,-100]
a.sort(key= lambda x: (x<0,abs(x)))
It gives me
[1, 5, 99, 100, -5, -7, -100]
It is sorted by positive/negative number and abs value.
How can I do the same thing in R? Without splitting into positive and negative numbers?
a = c(1,100,5,-5,-7,99,-100)
Use the order() function:
a = c(1,100,5,-5,-7,99,-100)
a[order(a < 0, abs(a))]
#> [1] 1 5 99 100 -5 -7 -100
Created on 2022-03-22 by the reprex package (v2.0.1)
Another possibility which is useful in some situations is to define an xtfrm method for a class. For example, if you know the values are all less than 1000, you could use
class(a) <- "classa"
xtfrm.classa <- function(x) {
(a < 0) + abs(a)/1000
}
sort(a)
#> [1] 1 5 99 100 -5 -7 -100
Created on 2022-03-22 by the reprex package (v2.0.1)
How about using factor with levels?
a <- c(1, 100, 5, -5, -7, 99, -100)
res <- factor(x = a, levels = unique(a[order(abs(a))]), ordered = TRUE)
res
# [1] 1 100 5 -5 -7 99 -100
# Levels: 1 < 5 < -5 < -7 < 99 < 100 < -100
Desired sorting order
unique(a[order(abs(a))])
# [1] 1 5 -5 -7 99 100 -100