波斯汪
is.element()使代码更具可读性,并且与%in%v <- c('a','b','c','e')is.element('b', v)'b' %in% v## both return TRUEis.element('f', v)'f' %in% v## both return FALSEsubv <- c('a', 'f')subv %in% v## returns a vector TRUE FALSEis.element(subv, v)## returns a vector TRUE FALSE