Data frames and matrices

We will now create a data frame, which is a collection of variables (vectors). We will create a vector of 1, 2, and 3 and another vector of 1, 1.5, and 2.0. Once this is done, the rbind() function will allow us to combine the rows:

> p = seq(1:3)

> p
[1] 1 2 3

> q = seq(1,2, by=0.5)

> q
[1] 1.0 1.5 2.0

> r = rbind(p,q)

> r
  [,1] [,2] [,3]
p    1  2.0    3
q    1  1.5    2

The result is a list of two rows with three values each. You can always determine the structure of your data using the str() function, which in this case, shows us that we have two lists, one named p and the other, q:

> str(r)
 num [1:2, 1:3] 1 1 2 1.5 3 2
 - attr(*, "dimnames")=List of 2
  ..$ : chr [1:2] "p" "q"
  ..$ : NULL

Now, let's put them together as columns using cbind():

> s = cbind(p,q)

> s
     p   q
[1,] 1 1.0
[2,] 2 1.5
[3,] 3 2.0

To put this in a data frame, use the as.data.frame() function. After that, examine the...