In R, what is a good way to aggregate String data

Question

In R (or S-PLUS), what is a good way to aggregate String data in a data frame?

Consider the following:

myList <- as.data.frame(c("Bob", "Mary", "Bob", "Bob", "Joe"))

I would like the output to be:

 [Bob,  3
  Mary, 1
  Joe,  1]

Currently, the only way I know how to do this is with the summary function.

> summary(as.data.frame(myList))

 Bob :3                                
 Joe :1                                
 Mary:1

This feels like a hack. Can anyone suggest a better way?

score 2 · Answer 1 · answered Jul 24 '09 at 18:47

2

This is a combination of the above answers (as suggested by Thierry)

data.frame(table(myList[,1]))

which gives you

  Var1 Freq
1  Bob    3
2  Joe    1
3 Mary    1

answered Jul 24 '09 at 18:47

andrewj

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It gives an error for me - a one liner based on Thierry's suggestion would be: as.data.frame(table(myList)) – bubaker Jul 26 '09 at 06:59
1

That's interesting. What kind of error message did you get? I just tried it without getting an error message. – andrewj Jul 26 '09 at 18:14
Scratch that - I tried it after defining myList as a list, not a data.frame – bubaker Jul 29 '09 at 07:16

bubaker · Accepted Answer · 2009-05-14T10:43:37.933

2

Using table, no need to sort:

ctable <- table(myList);
counts <- data.frame(Name = names(ctable),Count = as.vector(ctable));

edited May 14 '09 at 10:43

answered May 14 '09 at 07:39

bubaker

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you can simplify the last line to as.data.frame(ctable) Note that the semicolons are only needed if you put more than one command on a line. – Thierry Jul 24 '09 at 11:39

score 1 · Answer 3 · answered Sep 08 '18 at 04:02

1

Using data.table

myList <- data.frame(v1=c("Bob", "Mary", "Bob", "Bob", "Joe"))
library(data.table)
     v1 N
1:  Bob 3
2: Mary 1
3:  Joe 1

answered Sep 08 '18 at 04:02

Chriss Paul

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score 1 · Answer 4 · edited Jun 11 '14 at 07:04

1

Do you mean like this?

myList <- c("Bob", "Mary", "Bob", "Bob", "Joe")
r <- rle(sort(myList))
result <- as.data.frame(cbind(r$values, r$lengths))
names(result) <- c("Name", "Occurrences")
result
  Name Occurrences
1  Bob           3
2  Joe           1
3 Mary           1

edited Jun 11 '14 at 07:04

vrajs5

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answered May 13 '09 at 03:58

Jouni K. Seppänen

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score 0 · Answer 5 · answered Mar 19 '18 at 14:22

0

Using sqldf library:

require(sqldf)

myList<- data.frame(v=c("Bob", "Mary", "Bob", "Bob", "Joe"))
sqldf("SELECT v,count(1) FROM myList GROUP BY v")

answered Mar 19 '18 at 14:22

OmG

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In R, what is a good way to aggregate String data

5 Answers5