R从字符串中删除第一个字符
我可以从字符串中删除最后一个字符:
I can remove the last character from a string:
listfruit <- c("aapplea","bbananab","oranggeo")
gsub('.{1}$', '', listfruit)
但是我在尝试从字符串中删除第一个字符时遇到问题.还有第一个和最后一个字符.如果您提供帮助，我将不胜感激.
But I am having problems trying to remove the first character from a string. And also the first and last character. I would be grateful for your help.
如果我们需要去掉第一个字符，使用sub，匹配一个字符(.代表一个单个字符)，将其替换为 ''.
If we need to remove the first character, use sub, match one character (. represents a single character), replace it with ''.
sub('.', '', listfruit)
#[1] "applea" "bananab" "ranggeo"
或者对于第一个和最后一个字符，匹配字符串开头(^.)或字符串结尾(.$)的字符并替换它带有 ''.
Or for the first and last character, match the character at the start of the string (^.) or the end of the string (.$) and replace it with ''.
gsub('^.|.$', '', listfruit)
#[1] "apple" "banana" "rangge"
我们也可以将其作为一个组捕获并替换为反向引用.
We can also capture it as a group and replace with the backreference.
sub('^.(.*).$', '\\1', listfruit)
#[1] "apple" "banana" "rangge"
另一个选项是 substr
substr(listfruit, 2, nchar(listfruit)-1)
#[1] "apple" "banana" "rangge"