如何在R中统计多值分组字段中各变量的重复次数？

Hey there! The problem you're facing is that your sub column contains comma-separated combined values, so group_by(sub) treats each full string as a distinct group—hence why "A" and "A,B" get counted separately. Let's fix this so you get the individual counts you're after (A:3, B:3, C:2)!

Solution with dplyr + tidyr #

First, we'll use separate_rows() from the tidyr package to split those comma-separated values into individual rows, then count each unique value as usual.

1. First, let's replicate your dataset for testing:

mydata <- data.frame(
  num = 1:6,
  sub = c("A", "A,B", "C", "A", "B", "B,C")
)

2. Now run the processing code:

library(dplyr)
library(tidyr)

# Split comma-separated values into individual rows, then count
mydata2 <- mydata %>%
  separate_rows(sub, sep = ",") %>%
  group_by(sub) %>%
  summarise(n = n()) %>%
  ungroup() # Optional: removes grouping structure if you don't need it

# View the result
mydata2

This will give you exactly what you want:

# A tibble: 3 × 2
  sub       n
  <chr> <int>
1 A         3
2 B         3
3 C         2

Base R Alternative #

If you prefer not to load extra packages, you can use base R functions to achieve the same result:

# Split each string into a list, then flatten to a vector
sub_values <- unlist(strsplit(mydata$sub, ","))

# Count occurrences with table()
count_table <- table(sub_values)

# Convert to data frame if you want a structure similar to the dplyr output
as.data.frame(count_table)

This will return:

sub_values Freq
1          A    3
2          B    3
3          C    2

内容的提问来源于stack exchange，提问作者Jay Choi