How to create a boolean column that collectively responds to another column based on an ID column (using dplyr)?

Question

I am trying to create a table from this:

ID	Condition
1	B
1	B
1	A
2	B
2	B

To this:

ID	Condition	Flag
1	B	1
1	B	1
1	A	1
2	B	0
2	B	0

i.e. If the condition is A within any rows of the same ID, the flag would return 1 for all rows of the same ID.

I have tried something like this:

library(dplyr)

data %>%
   group_by(ID) %>%
   mutate(Flag = ifelse(Condition == 1, 1, 0)

But it just returns this:

ID	Condition	Flag
1	B	0
1	B	0
1	A	1
2	B	0
2	B	0

Sorry if this is unclear, if there is anything else you need from me for this question please let me know. Thanks.

Answer 1

ifelse is element-wise if-else statement, say, vectorized, which cannot give the desired output.

You can use if ... else ... instead of ifelse

> df %>% mutate(Flag = if (any(Condition == "A")) 1 else 0, .by = ID)
  ID Condition Flag
1  1         B    1
2  1         B    1
3  1         A    1
4  2         B    0
5  2         B    0

Or you can try %in%

> df %>% mutate(Flag = +("A" %in% Condition), .by = ID)
  ID Condition Flag
1  1         B    1
2  1         B    1
3  1         A    1
4  2         B    0
5  2         B    0