CODEWITHSUNDEEP
r
Anshul Saravgi
Anshul Saravgi

Reputation: 97

Check only 1st row of duplicated values for some condition

I am a newbie to R. Can someone help me with this

For below df, I need to check only the first row of each Item and if column "value = 0" then only I need to keep both the rows for that Item

df

Item    city   price  value
 A      Delhi   10      0
 A      Mumbai   5      2
 B      Delhi   10      1
 B      Mumbai   5      2

Here for Item A, we will check the first row and value =0 so we will keep both the rows of Item A. But when we check the first row of Item B there value=1 so we remove both the rows of Item B.

output

Item    city   price  value
 A      Delhi   10      0
 A      Mumbai   5      2

Upvotes: 1

Views: 47

Answers (2)

akrun
akrun

Reputation: 886938

We can group by 'Item', and filter the groups having the 'first' 'value' as 0

library(dplyr)
df %>%
     group_by(Item) %>%
     filter(first(value) == 0)
# A tibble: 2 x 4
# Groups:   Item [1]
#  Item  city   price value
#  <chr> <chr>  <int> <int>
#1 A     Delhi     10     0
#2 A     Mumbai     5     2

Or in base R

subset(df, Item %in% subset(df, !duplicated(Item) & !value)$Item)

data

df <- structure(list(Item = c("A", "A", "B", "B"), city = c("Delhi", 
"Mumbai", "Delhi", "Mumbai"), price = c(10L, 5L, 10L, 5L), value = c(0L, 
2L, 1L, 2L)), class = "data.frame", row.names = c(NA, -4L))

Upvotes: 2

Ronak Shah
Ronak Shah

Reputation: 388807

In base R, we can use ave 

df[with(df, ave(value == 0, Item, FUN = function(x) x[1L])), ]

#  Item   city price value
#1    A  Delhi    10     0
#2    A Mumbai     5     2

Upvotes: 1

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