在R中获取一个data.frame的样本 [英] getting a sample of a data.frame in R

问题描述

我在R中有以下数据框：

I have the following data frame in R:

id<-c(1,2,3,4,10,2,4,5,6,8,2,1,5,7,7)
date<-c(19970807,19970902,19971010,19970715,19991212,19961212,19980909,19990910,19980707,19991111,19970203,19990302,19970605,19990808,19990706)
spent<-c(1997,19,199,134,654,37,876,890,873,234,643,567,23,25,576)
df<-data.frame(id,date,spent)

我需要随机抽取3个客户（基于id），方式是客户的所有观察结果

I need to take a random sample of 3 customers (based on id) in a way that all observations of the customers be extracted.

推荐答案

您想在％和<$中使用％ c $ c> unique

df[df$id %in% sample(unique(df$id),3),]
##    id     date spent
## 4   4 19970715   134
## 7   4 19980909   876
## 8   5 19990910   890
## 10  8 19991111   234
## 13  5 19970605    23

使用 data.table 以避免 $ 引用

library(data.table)
DT <- data.table(df)

 DT[id %in% sample(unique(id),3)]
##    id     date spent
## 1:  1 19970807  1997
## 2:  4 19970715   134
## 3:  4 19980909   876
## 4:  1 19990302   567
## 5:  7 19990808    25
## 6:  7 19990706   576

确保您始终评估data.table中的表达式。

This ensures that you are always evaluating the expressions within the data.table.

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