在 R 编程中寻找元素的独特匹配 – char.expand()函数

R 语言中的char.expand()函数用于在第二个参数的元素中寻找其第一个参数的唯一匹配。如果成功，则返回此元素；否则，它执行第三个参数指定的动作。

Syntax: char.expand(input, target, nomatch = stop(“no match”))
Parameters: 
input: character string to be expanded 
target: character vector with the values to be matched against 
nomatch: an R expression to be evaluated in case expansion was not possible 
 

示例 1：

Python3

# R program to illustrate
# char.expand function
 
# Creating string vector
x <- c("sand", "and", "land")
 
# Calling char.expand() function
char.expand("a", x, warning("no expand"))
char.expand("an", x, warning("no expand"))
char.expand("and", x, warning("no expand"))

输出 ：

[1] "and"
[1] "and"
[1] "and"

示例 2：

Python3

# R program to illustrate
# char.expand function
 
# Creating string vector
x <- c("sand", "and", "land")
 
# Calling char.expand() function
char.expand("G", x, warning("no expand"))  

输出：

[1] NA
Warning message:
In eval(nomatch) : no expand