来自data.frames列表的示例

Question

I have the following list1 and list2 :

df1   <- data.frame(x=(1:3),Q=(3:5))
df2   <- data.frame(x=(1:3),Q=(3:5))
df3   <- data.frame(x=(1:3),Q=(3:5))
list1 <- list(df1,df2,df3)
list2 <- list(2,3,6)

I want to sample randomly from Q in each list1 element according to the corresponding value in list2

So I would sample from Q 2 times for the first pair of list elements.

So far I have managed:

df1   <- data.frame(x=(1:3),Q=(3:5))
z <- 2
sapply(1:z,function(i) sample(df1$Q,1))

but I am struggling at trying to mapply this across both all pairs of elements in both lists.

Answer 1

这是一个mapply方法：

mapply(function(x, y) sample(x[["Q"]], y, replace = TRUE), list1, list2)

Answer 2

Not sure if this is what you're after but it may help :

FUN <- function(x, z) sapply(1:z,function(i) sample(x[["Q"]], 1))
lapply(seq_along(list1), function(i) FUN(list1[[i]], list2[[i]]))