例如,这段代码df1 <- structure(list(Name = c("A", "B", "C"), Cricket = c("Y", "N",
"Y"), Football = c("Y", "Y", "N"), Swimming = c("N", "N", "Y"
)), class = "data.frame", row.names = c(NA, -3L))
显然是完全可以的。它需要一个double类型的参数。但是无法以任何方式使用该参数,因为未为其分配名称,因此没有可调用的名称。那在那里争论的意义何在?