如何在R中的另一个字符串的重复间隔处插入一个字符串

Question

我在 R 中有一个 x 元素的向量。我想重复这个向量，每 y 次重复插入另一个字符串。例如，我有下面的sequence 并想生成sequence_breaks，它有一个长度为4 的字符串，并且在每第4 项插入另一个字符串时重复。如何使 sequence_breaks 达到一定长度（比如 100）？

sequence <- c('a', 'b', 'c', 'd')
sequence_breaks <- c('a', 'b', 'c', 'break', 
                     'd', 'a', 'b', 'break',
                     'c', 'd', 'a', 'break',
                     'b', 'c', 'd',' break')

Answer 1

这是一种矢量化的基本 R 方式：

insert_text <- 'break'
n <- 100
insert_num <- 4

#Extend sequence till length n
new_vec <- rep(sequence, length.out = n)
#Create a sequence over new_vec
inds <- seq_along(new_vec)
#index to insert new text
b <- inds %% insert_num == 0
#Shift values by 1
new_vec1 <- new_vec[inds - cumsum(b)]
#insert the value at b
new_vec1[b] <- insert_text

#  [1] "a"     "b"     "c"     "break" "d"     "a"     "b"     "break"
#  [9] "c"     "d"     "a"     "break" "b"     "c"     "d"     "break"
# [17] "a"     "b"     "c"     "break" "d"     "a"     "b"     "break"
# [25] "c"     "d"     "a"     "break" "b"     "c"     "d"     "break"
# [33] "a"     "b"     "c"     "break" "d"     "a"     "b"     "break"
# [41] "c"     "d"     "a"     "break" "b"     "c"     "d"     "break"
# [49] "a"     "b"     "c"     "break" "d"     "a"     "b"     "break"
# [57] "c"     "d"     "a"     "break" "b"     "c"     "d"     "break"
# [65] "a"     "b"     "c"     "break" "d"     "a"     "b"     "break"
# [73] "c"     "d"     "a"     "break" "b"     "c"     "d"     "break"
# [81] "a"     "b"     "c"     "break" "d"     "a"     "b"     "break"
# [89] "c"     "d"     "a"     "break" "b"     "c"     "d"     "break"
# [97] "a"     "b"     "c"     "break"