Hello team,

I have a mind numbing loop to write and your help would be greatly appreciated!

I am trying to summarise grouped data by excluding each row iteratively and summing the mean of the remaining group, then rejoining to form a new data frame.

So, for instance with this mockup data...

```
x <- c("A","A", "B", "B")
y <- c(10:13)
xy <- data.frame(x,y) %>%
group_by(x) %>%
mutate(index = row_number(x)) %>%
ungroup()
xy$uniq_id<- with(xy, paste0(index, x))
```

Heres an image of the mockup data frame.

For 1A I the output value would be 11 because without row 1A, the sum of y for group A is 11. So, the value for 1B would be 13, and the value for 2B would be 12 ect.

Here is how I would do it manually for all the rows with index 1

```
xynew <- xy %>%
group_by(x) %>%
filter(index != "1") %>%
mutate(sum_Sepal = sum(y))
full_join(xy, xynew, by = "uniq_id")
```

My data frame has 38 groups with 1-70 rows per group so I cant do this manually!

Your help in trying to writing a loop for this would be amazing.

Please let me know if you have any questions:)

Looking forward to hearing from you.