如何将数值向量转换为二进制数？

Question

I converted a factor into a numeric vector ie from "Male" and "Female" to "1" and "2" with the R code, "as.numeric(data$Gender)". However, I would like to convert the numeric vector into binary numbers ie from "1" representing "Male" and "2" representing "Female", to "1" representing "Male" and "0" representing "Female". Could anybody please kindly advice me on how this could be done? Thank you very much, and your help is very much appreciated.

Answer 1

Here are three alternatives:

Sample data:

set.seed(1)
x <- sample(c("Male", "Female"), 10, TRUE)
x
#  [1] "Male"   "Male"   "Female" "Female" "Male"   "Female" "Female" "Female" "Female" "Male"  

Option 1: Use == (assumes that you only have these two options).

as.numeric(x == "Male")
#  [1] 1 1 0 0 1 0 0 0 0 1

---

Option 2: Use a named key.

key <- setNames(0:1, c("Female", "Male"))
key[x]
#   Male   Male Female Female   Male Female Female Female Female   Male 
#      1      1      0      0      1      0      0      0      0      1 

---

Option 3: Use factor specifying the labels.

factor(x, c("Male", "Female"), labels = c(1, 0))
#  [1] 1 1 0 0 1 0 0 0 0 1
# Levels: 1 0

Note that you'll still need as.numeric(as.character()) if you wanted a numeric vector:

as.numeric(as.character(factor(x, c("Male", "Female"), labels = c(1, 0))))
#  [1] 1 1 0 0 1 0 0 0 0 1