R apply如何熟练掌握

R语言里重要的三个函数我认为就是 apply, melt, dcast

掌握了才能入门R .

m = data.frame(m = c(1,2,3,4,5,6),n=c(3,4,5,7,8,9),t=c(4,5,6,7,8,9))

h = function(x,c1,c2){
v1 = median(as.numeric(x[c1]))
v2 = median(as.numeric(x[c2]))
v = v1/v2
return(v)
}

fold = apply(m,1,h,c(TRUE,TRUE,FALSE),c(TRUE,FALSE,TRUE))
fold = apply(m,1,h,c(1,2),c(1,3))