regex - 如何在R中使用RegEx替换字符串中的字符

Question

我正在尝试替换字符串中的某个字符，但由于这种模式反复出现，我曾想过使用 RegEx 迭代替换它(如果可能的话)。
例如考虑一个链接 http://www.bbc.co.uk/food/ingredients/by/letter/a

我要更换最后一个 'a' 和 'b'，然后是一个 'c'，一个 'd' 等等，直到 'z' 迭代。
与此一起使用的 RegEx 非常简单:
http:\/\/www\.bbc\.co\.uk\/food\/ingredients\/by\/letter\/[a-z]
这将验证字符串，但我想自动化链接生成过程。我对'R'很陌生，我想知道这样的事情是否可能。

Answer 1

您可以使用 paste0 创建如下链接列表:

l <- paste0("http://www.bbc.co.uk/food/ingredients/by/letter/", letters)

这导致以下列表:

> l
 [1] "http://www.bbc.co.uk/food/ingredients/by/letter/a"
 [2] "http://www.bbc.co.uk/food/ingredients/by/letter/b"
 [3] "http://www.bbc.co.uk/food/ingredients/by/letter/c"
 [4] "http://www.bbc.co.uk/food/ingredients/by/letter/d"
 [5] "http://www.bbc.co.uk/food/ingredients/by/letter/e"
 [6] "http://www.bbc.co.uk/food/ingredients/by/letter/f"
 [7] "http://www.bbc.co.uk/food/ingredients/by/letter/g"
 [8] "http://www.bbc.co.uk/food/ingredients/by/letter/h"
 [9] "http://www.bbc.co.uk/food/ingredients/by/letter/i"
[10] "http://www.bbc.co.uk/food/ingredients/by/letter/j"
[11] "http://www.bbc.co.uk/food/ingredients/by/letter/k"
[12] "http://www.bbc.co.uk/food/ingredients/by/letter/l"
[13] "http://www.bbc.co.uk/food/ingredients/by/letter/m"
[14] "http://www.bbc.co.uk/food/ingredients/by/letter/n"
[15] "http://www.bbc.co.uk/food/ingredients/by/letter/o"
[16] "http://www.bbc.co.uk/food/ingredients/by/letter/p"
[17] "http://www.bbc.co.uk/food/ingredients/by/letter/q"
[18] "http://www.bbc.co.uk/food/ingredients/by/letter/r"
[19] "http://www.bbc.co.uk/food/ingredients/by/letter/s"
[20] "http://www.bbc.co.uk/food/ingredients/by/letter/t"
[21] "http://www.bbc.co.uk/food/ingredients/by/letter/u"
[22] "http://www.bbc.co.uk/food/ingredients/by/letter/v"
[23] "http://www.bbc.co.uk/food/ingredients/by/letter/w"
[24] "http://www.bbc.co.uk/food/ingredients/by/letter/x"
[25] "http://www.bbc.co.uk/food/ingredients/by/letter/y"
[26] "http://www.bbc.co.uk/food/ingredients/by/letter/z"