Counting number of repetions in a particular column

Question

for eg: a dataframe "housing" has a column "street" with different street names as levels. I want to return a df with counts of the number of houses in each street (level), basically number of repetitions. what functions do i use in r?

score 0 · Accepted Answer · answered Jul 07 '20 at 14:18

0

This should help:

library(dplyr)

housing %>% group_by(street) %>% summarise(Count=n())

answered Jul 07 '20 at 14:18

Duck

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This saved me thanks! in addition, how do i ignore na values in housing while applying these arguments? – bverc Jul 07 '20 at 15:32
@bverc You could add a new pipe like `filter(!is.na(yourvariable))`. Let me know if I can help more! – Duck Jul 07 '20 at 15:36
Thank you, it's exactly what i needed – bverc Jul 07 '20 at 16:05

nya · Answer 2 · 2020-07-08T07:08:53.303

0

summary gives the first 100 frequencies of the factor levels. If there are more, try:

table(housing$street)

For example, let's generate one hundred one-letter street names and summarise them with table.

set.seed(1234)
housing <- data.frame(street = sample(letters, size = 100, replace = TRUE))
x <- table(housing$street)
x
# a b c d e f g h i j k l m n o p q r s t u v w x y z 
# 1 3 5 6 4 6 2 6 5 3 1 3 1 2 5 5 4 1 5 5 3 7 4 5 3 5

As per OP's comment. To further use the result in analyses, it needs to be included in a variable. Here, the x. The class of the variable is table, and it works in base R with most functions as a named vector. For example, to find the most frequent street name, use which.max.

which.max(x)
#  v 
# 22

The result says that the 22nd position in x has the maximum value and it is called v.

edited Jul 08 '20 at 07:08

answered Jul 07 '20 at 14:22

nya

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Thanks, that was so simple. is this in base r? – bverc Jul 07 '20 at 15:34
Also, I'm not able to perform any analysis using this method. for eg: to find the highest value – bverc Jul 07 '20 at 15:44
Simply send the table result into a variable and use it as a vector. I added an example to the response. – nya Jul 08 '20 at 07:09

score 0 · Answer 3 · answered Jul 07 '20 at 14:23

This can be done in multiple ways, for instance with base R using table():

table(housing$street)

It can also be done through dplyr, as illustrated by Duck.

Another option (my preference) is using data.table.

library(data.table)
setDT(housing)
housing[, .N, by = street]

Counting number of repetions in a particular column

3 Answers3