包含在该行中出现最多的字符串的新列

Question

Im trying to Create a column with the string that appears the most in the row and create another column with the number of times this most prevalent string appeared.

To facilitate my question this is what im trying to achieve:

My actual DF

What im trying to obtain: most prevalente category and count

example df: d

f <- data.frame(ID = 1:4,
           V1 = c("A","B","C","D"),
           V2 = c("A", "B","D","B"),
           V3 = c("A","C","D","B"))

Answer 1

Here is another way:

count <- sapply(apply(f[, -1], 1, table), max)
count
# [1] 3 2 2 2
category <- names(sapply(apply(f[, -1], 1, table), which.max))
category
# [1] "A" "B" "D" "B"
f2 <- data.frame(f, category, count)
f2
#   ID V1 V2 V3 category count
# 1  1  A  A  A        A     3
# 2  2  B  B  C        B     2
# 3  3  C  D  D        D     2
# 4  4  D  B  B        B     2

Answer 2

df <- data.frame(ID = 1:4,
                V1 = c("A","B","C","D"),
                V2 = c("A", "B","D","B"),
                V3 = c("A","C","D","B"))


library(data.table)
setDT(df)
other <- melt(df, id.vars = "ID", measure.vars = c("V1", "V2", "V3"))
other <- other[, .N, by = .(ID, value)]
colnames(other) <- c("ID", "category", "count")
other <- other[, .SD[which.max(count)], by = .(ID)]

res <- merge(df, other, by = c("ID"))
res

Answer 3

• We can use dplyr rowwise function to apply table to each row from V1:V3

library(dplyr)

df |> rowwise() |> 
      mutate(category = names(table(c_across(V1:V3)))[which.max(table(c_across(V1:V3)))] ,
      count = max(table(c_across(V1:V3))))

• Output

# A tibble: 4 × 6
# Rowwise: 
     ID V1    V2    V3    category count
  <int> <chr> <chr> <chr> <chr>    <int>
1     1 A     A     A     A            3
2     2 B     B     C     B            2
3     3 C     D     D     D            2
4     4 D     B     B     B            2