我想计算一列中重复的数量,并将它们添加到另一列到数据库。
例如,一些数据
a <- c(1,1,2,3,4,4)
b <- c("A","A","C","C","D","D")
df <- data.frame(a,b)
这是我正在寻找的结果:
a b count
1 1 A 1
2 1 A 2
3 2 C 1
4 3 C 1
5 4 D 1
6 4 D 2
试试这个:
df$count = sequence(rle(df$a)$lengths)
df
df$count <- with(df, ave(rep(1, nrow(df)), b, a, FUN = cumsum))
我们可以用data.table
做到这一点
library(data.table)
setDT(df)[, count := seq_len(.N), .(a, b)]
df
# a b count
#1: 1 A 1
#2: 1 A 2
#3: 2 C 1
#4: 3 C 1
#5: 4 D 1
#6: 4 D 2
我遇到了类似的问题,但只需根据1列中的信息计算重复数。 user7298145的答案适用于小型数据框,但是我的数据有大约20k行并且因错误而失败:
Error: memory exhausted (limit reached?)
Error during wrapup: memory exhausted (limit reached?)
所以我创建了一个for
循环,完成了这个技巧:
## order the values that are duplicated
primary_duplicated <- primary_duplicated1[order(primary_duplicated1$md5), ]
## create blank/NA column
primary_duplicated$count <- NA
## set first value as 1
primary_duplicated$count[1] <- 1
## set count of duplicates to 1 greater than the
## value of the preceding duplicate
for (i in 2:nrow(primary_duplicated)) {
if (primary_duplicated$md5[i] == primary_duplicated$md5[i-1]) {
primary_duplicated$count[i] <- primary_duplicated$count[i-1] + 1
} else {
## set the count value for the first incidence of
## a duplicate as 1
primary_duplicated$count[i] <- 1
}
}