R获取向量中每个单词的第一个、前两个、前三个字母的列表

# 定义一个包含多个单词的向量
words <- c("apple", "banana", "cat", "dog", "elephant")

# 获取每个单词的第一个字母的列表
first_letters <- sapply(words, function(word) substr(word, 1, 1))
print(first_letters)

# 获取每个单词的前两个字母的列表
first_two_letters <- sapply(words, function(word) substr(word, 1, 2))
print(first_two_letters)

# 获取每个单词的前三个字母的列表
first_three_letters <- sapply(words, function(word) substr(word, 1, 3))
print(first_three_letters)

[1] "a" "b" "c" "d" "e"
[1] "ap" "ba" "ca" "do" "el"
[1] "app" "ban" "cat" "dog" "ele"