CODEWITHSUNDEEP
rdplyr
Nathan123
Nathan123

Reputation: 763

Keep the key that has only one specific value in R

I have the following data frame

filen<-c('510-1','510-2','510-2','510-2','510-3','510-3','510-4')
disp<-c('g','ng','ng','ng','g','ng','ng')

df<-data.frame(filen,disp)


  filen disp
1 510-1    g
2 510-2   ng
3 510-2   ng
4 510-2   ng
5 510-3    g
6 510-3   ng
7 510-4   ng

Basically I want to isolate the file numbers where ng is the only type of disp associated with that filen. So that I get a dataset like this. How do I do this using dplyr

filen disp
510-2  ng
510-4  ng

Upvotes: 1

Views: 490

Answers (2)

akrun
akrun

Reputation: 887501

We can group by 'filen', filter the groups where all the 'disp' values are 'ng' and get the distinct rows

library(dplyr)
df %>%
   group_by(filen) %>%
   filter( all(disp == 'ng')) %>%
   distinct
# A tibble: 2 x 2
# Groups:   filen [2]
#  filen disp 
#   <fct> <fct>
#1 510-2 ng   
#2 510-4 ng

Or 

df %>% 
   distinct %>%
   group_by(filen) %>%
   filter(n_distinct(disp) == 1, disp == 'ng')

Or we can use data.table

library(data.table)
setDT(unique(df))[,  .SD[uniqueN(disp)==1 & disp == "ng"], filen]

Upvotes: 3

Ronak Shah
Ronak Shah

Reputation: 389135

Using base R, we one option can be to calculate the frequency of df using table, find the filen which have ng value greater than 0 and g value equal to 0 and keep only unique rows.

df1 <- as.data.frame.matrix(table(df))
unique(df[df$filen %in% rownames(df1)[df1$ng > 0 & df1$g == 0], ])

#  filen disp
#2 510-2   ng
#7 510-4   ng

Or with ave

unique(df[ave(df$disp == "ng", df$filen, FUN = all), ])

Upvotes: 1

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