remove a value with its counterpart conditional on an ID

Question

I have the following data frame

neto	damo
356	008
-356	008
-175	009
700	009
-700	009
250	009
-36	018
-36	018
-36	018

I want to eliminate the data with its counterpart conditioned to the ID and that it looks like this:

neto	damo
-175	009
250	009
-108	018

I have tried to put it in absolute values and leave the value that is unique, but this can produce an error if both are negative and should not be eliminated.

Answer 1

df %>%
  mutate(abs_neto=abs(neto)) %>%
  group_by(damo,abs_neto) %>%
  mutate(one_plus_one_minus= any(neto>=0) & any(neto<=0))%>%
  filter(n()==1 | !one_plus_one_minus)%>%
  ungroup 

   neto  damo abs_neto one_plus_one_minus
  <int> <int>    <int> <lgl>             
1  -175     9      175 FALSE             
2   250     9      250 FALSE             
3   250     9      250 FALSE

Answer 2

We may group by 'damo', remove the groups having only a single absolute 'neto' value, grouped by absolute of 'neto', filter out the groups having one value

library(dplyr)
df1 %>%
   mutate(s1 = sign(neto), absneto = abs(neto)) %>% 
   arrange(damo, desc(absneto), s1 == -1) %>% 
   group_by(damo) %>% 
   mutate(grp = cumsum(s1 > 0)) %>% 
   group_by(grp, .add = TRUE) %>% 
   filter(n_distinct(absneto) > 1|n_distinct(s1) == 1) %>% 
   group_by(s1, .add = TRUE) %>% 
   summarise(neto = sum(neto), .groups = "drop") %>%   
   select(-grp, -s1)

-output

# A tibble: 3 × 2
   damo  neto
  <int> <int>
1     9  -175
2     9   250
3    18  -108

data

df1 <-structure(list(neto = c(356L, -356L, -175L, 700L, -700L, 250L, 
-36L, -36L, -36L), damo = c(8L, 8L, 9L, 9L, 9L, 9L, 18L, 18L, 
18L)), class = "data.frame", row.names = c(NA, -9L))