Data Frame

A data frame is a special list in which every object has the same size.

Create a data frame

To create a data frame, the function data.frame() can be used as shown in the examples below. The data read from a file into R are often saved into a data frame.

> a <- 1:3
> b <- 4:6
> d <- 7:9
> y <- data.frame(a,b,d)
> y
  a b d
1 1 4 7
2 2 5 8
3 3 6 9
> 

Access the components of a data frame

The same methods for access the objects in a list can be used for a data frame. For example, y$a will access a in the data frame. The R function attach() can conveniently copy all objects in a data frame into R workspace so that they can be accessed using their names directly. To remove those objects, the function detach() can be used. Some examples are given below.

> y <- data.frame(a=1:4,b=5:8,d=9:12)
> y
  a b  d
1 1 5  9
2 2 6 10
3 3 7 11
4 4 8 12
> 
> y$a
[1] 1 2 3 4
> 
> attach(y)
> b
[1] 5 6 7 8
> 
> detach(y)
> b
Error: object 'b' not found
Execution halted