How to compare two factors in a single column in a dataframe based on the values in another column and delete them if they don't match

Question

I am trying to compare two factors based on the values (date in this case) in another column. If they don't match I would like to delete the row.

example:

>head(data)
 light date
1 0    20190314
2 0    20190317
3 1    20190314
4 0    20190318
5 1    20190316
6 1    20190318
7 1    20190314

So I would like the result to be:

>head(data)

 light date
1 0    20190314
2 1    20190314
3 0    20190318
4 1    20190318
5 1    20190314

Thanks in advance

Answer 1

Here is one solution.

Input

tribble(~light, ~date,
"0","20190314",
"0","20190317",
"1","20190314",
"0","20190318",
"1","20190316",
"1","20190318",
"1","20190314"
) ->d

Code

library(dplyr)
d %>% group_by(date) %>% # group by date
  mutate(is_keep = if_else("0" %in% light & "1" %in% light, 1,0)) %>% # create a temporary column to keep track if date has both 0 and 1. 
  filter(is_keep==1) %>% # filter out rows to keep
  select(-is_keep) %>% # remove temp column
  ungroup() #ungroup df

Output

  light date    
  <chr> <chr>   
1 0     20190314
2 1     20190314
3 0     20190318
4 1     20190318
5 1     20190314