how to select rows that have same absolute value of a number

Question

    transaction  | sum
    -------------|--------
 1 | refill      | 1450
 2 | write-off   | -1450
 3 | refill      | 3500

I want to choose only those values that have same absolute value of a number. There are rows 1 and 2. How can I do it in R?

What happens if there is a third row with `1450` or `-1450` ? — Tim Biegeleisen, Jul 20 '18 at 09:30
oh, I forgot to mention that there is a user id too, so it should be selected within transactions of same user id — nurma_a, Jul 20 '18 at 09:33
nurma please make sure to have a reproducible example and to add the DESIRED RESULT to your question. — Andre Elrico, Jul 20 '18 at 09:34

score 1 · Accepted Answer · answered Jul 20 '18 at 09:54

Another method, using Andre's dataset:

df1<-data.frame(index=1:6,sum=c(1,2,3,-1,3,4))
df1[duplicated(abs(df1$sum)) | duplicated(abs(df1$sum), fromLast = T),]

This is based on scanning for duplicates in forward order, then in reverse order, and then ORing the result to match all duplicated cases. As described here: Find indices of duplicated rows

score 0 · Answer 2 · answered Jul 20 '18 at 09:41

df1<-
data.frame(index=1:6,sum=c(1,2,3,-1,3,4))

#  index sum
#1     1   1
#2     2   2
#3     3   3
#4     4  -1
#5     5   3
#6     6   4

keep <- abs(df1$sum) %in% abs(df1$sum[duplicated(abs(df1$sum))])

df1[keep,]

#  index sum
#1     1   1
#3     3   3
#4     4  -1
#5     5   3

how to select rows that have same absolute value of a number

2 Answers2