Using loop and subset to create different data.frames

Question

I have a data.frame in R. I want to create three different data.frame using a loop and subset function. I have a large data.frame, but what I need is in the example below:

sex<-c("M","M","M","F","M","F")
age<-c(20,18,17,20,18,17)
name<-c("John", "Joseph", "Bill", "Sarah", "Robert", "Dana")
data<-data.frame(sex, age, name)

>data
        sex  age   name
    1   M    20    John
    2   M    18    Joseph
    3   M    17    Bill
    4   F    20    Sarah
    5   M    18    Robert
    6   F    17    Dana

What I want is:

>age17
      sex   age   name
    1 M     17    Bill
    2 F     17    Dana

>age18
      sex   age   name
    1 M     18    Joseph
    2 M     18    Robert


>age20
      sex   age   name
    1 M     20    John
    2 F     20    Sarah

I can use the commands below:

>age17<-subset(data, data[,2]==17)
>age18<-subset(data, data[,2]==18)
>age20<-subset(data, data[,2]==20)

But it is possible to use a loop to reduce the size of commands?

I think you might enjoy the function split.

joran
– joran

2012-07-13 15:38:20 +00:00
Commented Jul 13, 2012 at 15:38 — joran
– joran, Commented Jul 13, 2012 at 15:38

Andrie · Accepted Answer · 2012-07-13 15:38:47Z

6

Use split:

x <- split(data, data$age)

x
$`17`
  sex age name
3   M  17 Bill
6   F  17 Dana

$`18`
  sex age   name
2   M  18 Joseph
5   M  18 Robert

$`20`
  sex age  name
1   M  20  John
4   F  20 Sarah

You now have a list of data frames, and you can access the elements of the list using any of the extract operators, i.e. $, [ or [[.

For example, the first element:

x[1]
$`17`
  sex age name
3   M  17 Bill
6   F  17 Dana

Or the element with name 17. But notice that you have to use backticks to refer to these names, since names starting with numerals are not standard:

x$`17`
  sex age name
3   M  17 Bill
6   F  17 Dana

answered Jul 13, 2012 at 15:38

Andrie

180k52 gold badges456 silver badges504 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

GSee Over a year ago

This will assign the data.frames to variables age17, age18, etc. invisible(lapply(split(data, data$age), function(x) { assign(paste0("age", x$age[1]), x, pos=.GlobalEnv) }))

Collectives™ on Stack Overflow

Using loop and subset to create different data.frames

1 Answer 1

1 Comment

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Related