R语言：统计数据框特定值生成布尔计数表及报错解决

Hey there! Let's sort out this counting problem for you. First, let's recap your data setup so we're all on the same page:

library(dplyr)
df <- data.frame(letters = letters) %>% 
  mutate(letters = as.character(letters))
df[3,1] <- "" 
df[5,1] <- "" 
df[8,1] <- "Unknown"

Why your original code failed #

The error happens because which() expects a single logical vector as input, but your syntax is passing multiple arguments incorrectly. Instead of trying to filter the existing table(df) output, it's simpler to first create a logical flag for your target values, then count those flags.

Solution 1: Base R (simple & straightforward) #

First, create a logical vector that marks whether each value is either "" or "Unknown", then use table() to count the TRUE/FALSE cases:

# Create a logical indicator for target values
is_match <- df$letters %in% c("", "Unknown")

# Count the occurrences
result_table <- table(is_match)
result_table

This will output exactly what you're looking for:

is_match
FALSE  TRUE 
   23     3 

If you want the labels to be capitalized ("False" instead of "FALSE", "True" instead of "TRUE"), you can adjust the factor levels:

result_table_named <- table(
  factor(is_match, 
         levels = c(FALSE, TRUE), 
         labels = c("False", "True"))
)
result_table_named

Solution 2: Tidyverse/dplyr approach #

If you prefer working with dplyr, you can use mutate() to add the logical flag and count() to tally, or directly summarize the counts:

Option 2a: Using count()

df %>%
  mutate(is_match = letters %in% c("", "Unknown")) %>%
  count(is_match) %>%
  mutate(is_match = ifelse(is_match, "True", "False"))

Option 2b: Direct summary (gives exact "True:3, False:23" style output)

df %>%
  summarise(
    True = sum(letters %in% c("", "Unknown")),
    False = n() - True
  )

This will return a data frame with one row and two columns, showing your desired counts directly.

内容的提问来源于stack exchange，提问作者Doug Fir