How do I get the most frequent entry in R?-CodePudding

How do I get the most frequent entry in R?

For example if I would have data in two columns:

Name-City

A-New York

A-New York

A-Montreal

A-New York

B-Chicago

B-Chicago

B-New York

B-Detroit

I would like to get a dataframe with:

Name-City

A-New York

B-Chicago

So it should have every unique entry in "Name" with the most frequent entry in "City".

My idea would be something like:

df %>%
 group_by(Name) %>%
 count(City)

CodePudding user response：

Using mtcars, let's say we want to find the most frequent number of gears for each number of cylinders:

library(tidyverse)

mtcars %>% group_by(cyl, gear) %>% 
  summarize(count = n()) %>% 
  filter(count == max(count))

# A tibble: 3 x 3
# Groups:   cyl [3]
    cyl  gear count
  <dbl> <dbl> <int>
1     4     4     8
2     6     4     4
3     8     3    12

First we need to count how many occurrences of each cylinder/gear combination there are. Then we can filter to the largest (i.e. most frequent) occurrence.

CodePudding user response：

library(dplyr)

df %>%
  group_by(Name) %>% 
  count(City) %>%
  top_n(1)

# Selecting by n
# # A tibble: 2 x 3
# # Groups:   Name [2]
#   Name  City         n
#   <chr> <chr>    <int>
# 1 A     New York     3
# 2 B     Chicago      2