r语言 - 如何防止 tidyr 的单独函数拉入行号然后删除数据

Question

每当遇到大写字母时，我试图写一行代码来分隔文本字符串，而不删除该字母。我采取的方法如下：

set.seed(1)
# create a dataframe of fused alpha numeric codes that I wish to separate
df1 <- as.data.frame(matrix(
paste0(sample(LETTERS, 20, replace = TRUE), sample(seq(1, 7, 0.1), 20, replace = TRUE)), 
nrow = 10)) %>% unite(col = "ab", sep = "")
df1
# Add a space (" ") before any captial letter encountered
df2 <- df1 %>% mutate(ab = gsub('([[:upper:]])', ' \1', ab))
df2
# use separate to split the column based on the space
df3 <- df2 %>% separate(col=ab, into=c("a", "b"), sep = " ")
df3

当我运行separate时，我收到一个警告，并且输出不正确：

#Warning message:
#Expected 2 pieces. Additional pieces discarded in 10 rows [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. 
#> df3
#   a    b
#1      Y3
#2    D4.6
#3      G5
#4    A3.4
#5    B5.5
#6    W4.6
#7    K4.6
#8    N4.3
#9    R5.1
#10   S3.4

用于列"；a"；已放置在"；b"；，而那些旨在"；b"；似乎已完全删除。

Answer 1

另一个选项是从一开始就制作更精确的正则表达式。

例如

df1 |>
separate(col  = ab,
into = c("a", "b"),
sep  = "(?<=\d)(?=[[:upper:]])")

输出：

a    b
1  B1.8 Z4.3
2    M5 U6.7
3    N5 Q5.1
4  V4.9 B6.5
5    N4 V1.2
6  H2.8 J5.1
7  Q3.6 J1.3
8  J3.8 G2.9
9  B1.2 W4.7
10 L1.6 O3.5

Answer 2

这是因为在第一个字母之前创建了一个空白：要删除它，可以使用trimws或str_trim:

df1 %>% 
mutate(ab = trimws(gsub('([[:upper:]])', ' \1', ab))) %>%
separate(col=ab, into=c("a", "b"), sep = " ")

a    b
1    Y3 A5.3
2  D4.6 U2.4
3    G5 U4.2
4  A3.4 J2.9
5  B5.5 V4.4
6  W4.6 N1.5
7  K4.6 J1.9
8  N4.3 G5.1
9  R5.1 I4.7
10 S3.4 O5.6