在R中，增加列表与增加向量一样低效吗？

Question

some_list <- list()

for (i in 1:1000) {
    some_list[[i]] <- i
}

我想知道，如果some_list成为矢量，这是否效率不高？

Answer 1

答案似乎是“是”。您可以对其进行基准测试。

f = function() {
  some_list <- list()
  for (i in 1:100000)
    some_list[[i]] <- i
}

g = function() {
  some_vector <- c()
  for (i in 1:100000)
    some_vector[i] <- i
}

h = function() {
  some_list <- vector("list", 100000)
  for (i in 1:100000)
    some_list[[i]] <- i
}

k = function() {
  some_vector <- integer(100000)
  for (i in 1:100000)
    some_vector[i] <- i
}

microbenchmark::microbenchmark(f(), g(), h(), k(), times = 10)
Unit: milliseconds
 expr       min        lq      mean    median        uq      max neval
  f() 27.723670 28.058052 31.043727 28.812197 33.973669 38.58484    10
  g() 20.699626 21.235849 23.029765 21.531695 26.419720 28.04681    10
  h()  7.056399  7.151585  7.887856  7.356198  7.936945 10.80190    10
  k()  6.025570  6.076456  7.194970  6.408183  7.808957 11.00644    10