我正在使用下面的代码对一个人口进行分层随机抽样，之前根据性别和地区建立了目标。可以看到，相同的代码重复了三次（每次使用rbind）。有没有办法编写一个循环函数，可以重复这个过程，这样我就不必写几次了？

library(tidyverse)
population<- data.frame(region=rep(c("North", "South", "North", "South"),50000),
                        sex=rep(c("Male", "Female", "Female", "Male"),50000))

targets<- data.frame(region=c("North", "South", "North", "South"),
                     sex=c("Male", "Female", "Female", "Male"),
                     total=c(20,25,20,30)) 

n=0
n=n+1
sample<- population %>% filter(region==targets$region[[1]], 
                           sex==targets$sex[[1]]) %>% 
  slice_sample(n=targets$total[[1]])
n=n+1
sample<- sample %>%  rbind(population %>% filter(region==targets$region[[n]], 
                               sex==targets$sex[[n]]) %>% 
  slice_sample(n=targets$total[[n]]))
n=n+1
sample<- sample %>%  rbind(population %>% filter(region==targets$region[[n]], 
                               sex==targets$sex[[n]]) %>% 
  slice_sample(n=targets$total[[n]]))
n=n+1
sample<- sample %>%  rbind(population %>% filter(region==targets$region[[n]], 
                               sex==targets$sex[[n]]) %>% 
  slice_sample(n=targets$total[[n]]))