Example 1

The first example looks like this:

.1                      10              7
.2                      10              15
.3                      10              19
.4                      10              23
.1                      20              15
.2                      20              13
.3                      20              26
.4                      20              38
.1                      30              21
.2                      30              28
.3                      30              31
.4                      30              47

Reading across, this says that the first patient took a dose of .1, with 10 units of water, and experienced 7 units of relief.

We can read this into S-PLUS (calling the data frame ``ex1''):

> ex1 <- read.table("example1")
> ex1
    V1 V2 V3
 1 0.1 10  7
 2 0.2 10 15
 3 0.3 10 19
 4 0.4 10 23
 5 0.1 20 15
 6 0.2 20 13
 7 0.3 20 26
 8 0.4 20 38
 9 0.1 30 21
10 0.2 30 28
11 0.3 30 31
12 0.4 30 47

S-PLUS reads the data into a 12-row, 3-column matrix (just like the file) and labels the rows (the observations) 1 through 12 and the columns (the variables) V1, V2 and V3. These columns can be given more descriptive names by making an assignment to the names attribute of ex1.

> names(ex1) <- c("Dose","Water","Relief")

And to check that it worked:

> names(ex1)
[1] "Dose"   "Water"  "Relief"
> ex1
   Dose Water Relief
 1  0.1    10      7
 2  0.2    10     15
 3  0.3    10     19
 4  0.4    10     23
 5  0.1    20     15
 6  0.2    20     13
 7  0.3    20     26
 8  0.4    20     38
 9  0.1    30     21
10  0.2    30     28
11  0.3    30     31
12  0.4    30     47

We could have saved a step by specifying the column names in the read.table command:

> ex1 <- read.table("example1", col.names=c("Dose", "Water", "Relief"))