# Tagging values unique to a group in a dataframe
**URL:** https://discourse.julialang.org/t/tagging-values-unique-to-a-group-in-a-dataframe/97967
**Category:** Data
**Created:** [April 26, 2023, 8:11pm UTC](https://discourse.julialang.org/t/tagging-values-unique-to-a-group-in-a-dataframe/97967 "2023-04-26T20:11:37Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@George9000](https://discourse.julialang.org/u/George9000)
#### Post date: [April 26, 2023, 8:11pm UTC](https://discourse.julialang.org/t/tagging-values-unique-to-a-group-in-a-dataframe/97967/1 "2023-04-26T20:11:37Z")
Say that I have a dataframe:
```julia
function exampl()
grp = Int8[]
for i in 1:5
grp = append!(grp, fill(i, 7))
end
values = Int8[]
for i in 1:7
values = append!(values, rand(1:15, 5))
end
df = DataFrame(grp = grp, values = values)
gdf = groupby(df, :grp)
combine(gdf, :values => unique)
end
```
```julia
julia> exampl()
25×2 DataFrame
Row │ grp values_unique
│ Int8 Int8
─────┼─────────────────────
1 │ 1 11
2 │ 1 3
3 │ 1 9
4 │ 1 6
5 │ 1 1
6 │ 1 15
7 │ 2 8
8 │ 2 2
9 │ 2 10
10 │ 2 11
11 │ 2 3
12 │ 3 5
13 │ 3 15
14 │ 3 1
15 │ 3 4
16 │ 3 14
17 │ 4 12
18 │ 4 15
19 │ 4 10
20 │ 4 4
21 │ 4 14
22 │ 5 3
23 │ 5 8
24 │ 5 1
25 │ 5 4
```
How would I create a third column `unique_to_group`, a Boolean value that shows if the value in each row is unique to only that group compared with other groups. Example: row 3, with value 9 would be flagged as `true` in the new column as it is unique to grp 1 only. I have been trying `setdiff!` approaches but haven’t been able to make it work.
---
### Author:  [@bertschi](https://discourse.julialang.org/u/bertschi)
#### Post date: [April 26, 2023, 8:27pm UTC](https://discourse.julialang.org/t/tagging-values-unique-to-a-group-in-a-dataframe/97967/2 "2023-04-26T20:27:30Z")
If I understand correctly, turning the problem around should work:
```julia
using Chain
df = exampl()
@chain df begin
groupby(:values_unique)
transform(:grp => (x -> length(unique(x)) == 1) => :ha)
end
```
---
### Author:  [@George9000](https://discourse.julialang.org/u/George9000)
#### Post date: [April 27, 2023, 1:59am UTC](https://discourse.julialang.org/t/tagging-values-unique-to-a-group-in-a-dataframe/97967/3 "2023-04-27T01:59:12Z")
Yes! Indeed, turning the problem around. Thank you so much.