How to code to get an output vector list of unique elements based satisfying two conditions?-CodePudding

I'm trying to get list of uniques elements based on conditions of two columns in R.

For example, I have 4 groups and I want to get unique list of names of participants who are in group-1.

This requires to specify the two conditions in the code:

Unique(df$participants XXX_group_XXX).

How to code this condition specifically to get the output vecort list satisfying both conditions?

CodePudding user response：

Would this work for you? I need to create a data frame first. Then I filter for the group you wish to see and get the unique values per group.

library(dplyr)
    
seed <- 123
# create some data    
data <- data.frame(
         name = sample(LETTERS, size = 100, replace = TRUE),
         group = sample(c(1, 2, 3, 4), size = 100, replace = TRUE)
    )
    
# base R
unique(data[data$group == 1, 1])
# or:
unique(data[data$group == 1, "name"])
    
# tidyverse
data %>%
    filter(group == 1) %>%
    distinct(name) %>%
    pull() # if you want a vector to be returned

CodePudding user response：

A simple solution using only base R:

set.seed(7*11*13)

name <- sample(LETTERS[1:10], 100, replace=TRUE)
G <- sample(1:5, 100, replace=TRUE)
 
U <- tapply(name, G, unique) 

> U
$`1`
[1] "G" "F" "D" "B" "J" "A" "E" "H" "C"

$`2`
[1] "C" "J" "D" "B" "F" "G"

$`3`
[1] "C" "G" "H" "D" "F" "E" "I" "B" "J"

$`4`
[1] "F" "B" "G" "E" "I" "C" "H" "D" "J"

$`5`
[1] "G" "D" "A" "H" "F" "E" "B" "J" "C"