为组 R 生成随机数

Question

I want to generate the same random number for groups. Unfortunately, my following code generates random number for each row.

randomised <- data %>%
  group_by(`ID`)%>%
  mutate(random = sample(1:100,n(), replace = TRUE))

Any help is appreciated.

Answer 1

You should just select 1 value from sample which will be recycled for all the values in the group.

library(dplyr)
data %>% group_by(ID)%>% mutate(random = sample(100,1))

Or in base R :

data$random <- with(data, ave(seq_along(ID), ID,FUN = function(x) sample(100, 1)))

Answer 2

data.table一个选项：

setDT(data)[, random := sample(100, 1), ID]

Answer 3

Not sure why we need this, if we are trying to anonymise the IDs ( cyl column in mtcars example data), then this is pretty random to me:

library(dplyr)

mtcars %>% 
  mutate(random = as.integer(as.factor(cyl)))