CODEWITHSUNDEEP
rstringdataframecountunique
user2113499
user2113499

Reputation: 1021

Counting number of specific strings in an R data frame

I have a data frame that has many columns, but the two columns I am interested in are major and department. I need to find a way to count the number of specific entries in a column. So my data frame looks something like 

student_num    major          dept
123            child          education
124            child          education
125            special        education
126            justice        administration
127            justice        administration
128            justice        administration
129            police         administration
130            police         administration

What I want is a student count for each major and department. Something like

education   child   special    administration    justice    police
3           2       1          5                 3          2

I have tried several methods but nothing is quite what I need. I tried using the aggregate() function and the ddply() from plyr but they give me department as two - for two unique entries, education and administration. How can I count each unique entry and not how many unique entries there are?

Upvotes: 2

Views: 19842

Answers (2)

www
www

Reputation: 39174

# Create example data frame
dt <- read.table(text = "student_num    major          dept
123            child          education
                 124            child          education
                 125            special        education
                 126            justice        administration
                 127            justice        administration
                 128            justice        administration
                 129            police         administration
                 130            police         administration",
                 header = TRUE, stringsAsFactors = FALSE)

# Select columns
dt <- dt[, c("major", "dept")]

# Unlist the data frame
dt_vec <- unlist(dt)

# Count the number
table(dt_vec)

dt_vec
administration          child      education        justice         police 
             5              2              3              3              2 
       special 
             1

Upvotes: 2

arcvetkovic
arcvetkovic

Reputation: 126

You can try:

library(dplyr)
count(my_dataframe, major)
count(my_dataframe, dept)

Upvotes: 9

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