从向量中为data.table的每一行选择一个随机元素 [英] Pick one random element from a vector for each row of a data.table

问题描述

我有一个名称的数据框。和我有一个不同的食物的矢量。我要从该向量中为每个名称随机选择一个元素，以便data.table如下所示。

I have a dataframe of names. And I have a vector of different food items. I want to pick one element from that vector randomly for each Name so that the data.table looks like below.

x<- c("apple","pepsi","rice","coke","banana","butter","bread")

library(data.table)

dt <- fread('

Name  NextItem
John   rice
Logan  butter
Sarah  bread
Vinny  rice
')

我想替换取样。我尝试过

I want the sampling with replacement. I have tried

dt [，NextItem：= sample（x，1）] 项目（向量元素）为大家，而不是不同的随机元素像上述例子。

dt[,NextItem:= sample(x,1)] but it samples the same food item(vector element) for everyone, not different random elements like aforementioned example.

推荐答案

我们可以使用group by选项，然后执行 sample p>

We can use group by option and then do sample

dt[, NextItem := sample(x, 1), by = Name]

或者您也可以使用 .N 而不是 / code>

Or you can also do this with .N instead of by

dt[, NextItem := sample(x, .N, replace = TRUE)]

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