各位老师好，小弟有关于如何有条件的识别重复数据：
1、看到之前论坛其他老师贡献的语句，可以实现同时以id和weight来进行识别，是否为重复项，并保留不重复的值；
library(dplyr)
a1<-a%>%
group_by(id,weight,) %>%
  filter(row_number() == 1) %>%
  ungroup()
2、我的问题是，能否将weight这一栏设置一个范围，比如当id相同，但是weight之间相差5以内认为是重复记录，而大于5后认为是不重复的记录（如图1）；
3、当id重复多余2个以上，又该如何处理（数据如图3）；

望有老师能解答，万分谢谢~

#构建数据框（图1）#
c1<-c(1:6)
c2<-c("30040","30040","30041","30041","30042","30043")
c3<-c("45","46","50","70","45","60")
a=data.frame(c1,c2,c3)
names(a)<-c("num","id","weight")

#构建数据框（图2）#
c1<-c(1:7)
c2<-c("30040","30040","30041","30041","30041","30042","30043")
c3<-c("45","46","50","70","55","45","60")
a1=data.frame(c1,c2,c3)
names(a1)<-c("num","id","weight")