Using R for Introductory Statistics : John Verzani

Appendix E 388String$defineMethod("split".function(by="") {unlist(strsplit(string,by))})setMethod("/","String",function(e1,e2) el$split(e2))Again strsplit () does the hard work. We defined a new method, split, but didn’t have toworry about matching the formal arguments of the previously defined split () function (anS3 generic method). However, when we use the S4 style to use the "/" syntax, we needour function to match the formal arguments it uses (e1,e2).We can now “divide” our strings as follows:> flanders=String$new("Ned, Maude, Todd, Rod")> flanders$split() # into character bydefault[1] "N" "e" "d" "," " " "M" "a" "u" "d" "e" "," " ""T" "o" "d"[16] "d" "," " " "R" "o" "d"> flanders/" "[1] "Ned," "Maude," "Todd," "Rod"As mentioned, when using OOP we can modify the object in place. For example, wemight want to make the string uppercase. This can be done by defining an up casemethod as follows:String$defineMethod("upcase",function() {set.string(toupper(string))})Applying the function gives> flanders$upcase()> flandersNED, MAUDE, TODD, RODThe upcase () method uses both the string variable and the set. str ing () function, whichare created from the field names. Simple assignment to string will not work, although the