R SAMPLING BASED ON RULE

问题

data1 = data.frame("id" = c("f","e","b","a","e","d","e","f","c","d","d","c","d","b","e","b","d","b","e","e","b","a","b","e","a","d","a","d","b","f","b","e","b","d","e","d","b","e","f","a","b","b","f","e","c","a","b","d","c","d","e","e","f","e","a","b","b","c","b","a","b","f","a","b","c","e","d","a","e","d","a","f","b","d","e","b","f","e","f","f","c","b","f","c","b","e","e","f","e","b","f","f","b","e","c","a","e","c","d","b"),
                   "class" = c(4,1,2,4,1,4,3,2,1,1,2,4,2,2,3,1,4,1,2,4,2,2,1,1,1,3,4,4,4,3,3,2,3,2,2,2,3,4,1,2,4,1,1,3,3,2,2,2,4,4,3,3,1,1,4,2,3,2,4,1,4,3,2,3,4,3,3,2,3,4,4,1,4,1,2,3,4,1,2,1,3,4,4,3,1,2,4,2,3,2,4,2,2,1,1,4,1,3,1,1),
                   "score" = c(59,65,61,64,91,91,70,90,64,87,51,54,92,76,75,78,55,99,66,57,88,89,77,66,100,92,80,84,52,66,59,71,56,88,51,97,65,89,65,67,52,57,51,63,67,79,51,90,79,54,90,55,90,72,64,52,95,61,87,54,91,75,80,93,53,81,87,85,84,84,81,93,100,51,70,64,51,54,83,96,65,61,53,80,68,73,52,57,96,55,63,97,94,77,63,98,85,97,65,77))


data2 = data.frame("class" = c(1,2,3,4),
                   "s" = c(2,5,3,1))

I have dataset 'data1'. I want to create 'data2' by looking at the 'class' col in 'data2' and sampling randomly 'count' rows. So then: in data2 the 'count' for "c" is 3; so then sample 3 rows for each 'id' in class 'c' in data1.

回答1:

Using dplyr, one way would be to join df and df.1 based on class, group_by class and sample rows from df.1 based on count column in df.1.

library(dplyr)
set.seed(123)

df.1 %>%
  rename_at(ncol(.), ~'sample') %>%
  right_join(df, by = 'class') %>%
  group_by(class) %>%
  sample_n(sample) %>%
  select(names(df))

#     id class count
#  <int> <fct> <dbl>
#1     3 a         8
#2     3 b         5
#3     4 b         6
#4     2 b         9
#5     1 b         4
#6     2 c         4
#7     4 c         3
#8     3 c         3

Hence, we get 1 row from class A, 4 from B and 3 from C.

来源：https://stackoverflow.com/questions/60123851/r-sampling-based-on-rule

标签

dplyr

sample