如何从 R 中的交叉表（或 n 维数组中的 dimname 组）中采样 rowname-colname 对？

Question

In R it is quite trivial to "collapse" an n-dimensional array into a one-dimensional column vector and sample from that using eg sample() function in base R.

However, I would like to sample dimnames-groups (ie rowname-colname pairs in case of a two-dimensional array) based on the frequencies.

Let's have an example, and assume we have a following crosstab (the data (n=70) is randomly generated):

	Man	Woman
Smoking	10	20
Non-smoking	15	25

How do I sample from this that I get:

• "Smoking Man" with probability: 10 / 70
• "Non-smoking Man" with probability: 15 / 70
• "Smoking Woman" with probability: 20 / 70
• "Non-smoking Woman" with probability: 25 / 70

The easiest way would probably be grouping the dimnames (somehow), and use this as the first argument of sample function ie:

sample(x = vectorOfGroupedDimnames, size = 1, prob = c(crosstabAsMatrix))

Yes, and I know that the variable vectorOfGroupedDimnames can be formed using nested for loops, but there has to be more elegant ways of doing this.

So what is the easiest way to do this? Thanks.

Answer 1

Maybe this will help you

library(dplyr)

data <-
  structure(c(25L, 20L, 15L, 10L), .Dim = c(2L, 2L), .Dimnames = list(
    smoke = c("Non-smoking", "Smoking"), sex = c("Female", "Male"
    )), class = "table")

data %>% 
  as_tibble() %>% 
  sample_n(size = 1,weight = n,replace = TRUE)