Seeking a unique match of elements in R Programming – char.expand() Function
char.expand() function in R Language is used to seek a unique match of its first argument among the elements of its second. If successful, it returns this element; otherwise, it performs an action specified by the third argument.
Syntax: char.expand(input, target, nomatch = stop(“no match”))
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
 "and"  "and"  "and"
 NA Warning message: In eval(nomatch) : no expand