Q:

How does this code of R means?

The first line import the data file and the second one suppose to create a subset of 100 data
i) Assign the data to a matrix, 
e.g.  using
the.data <- as.matrix(read.table("filename.txt"))

(ii) Your variable of interest is Y-Rank ID.Generate a subset of 100 data, e.g.  using:
**my.data <- the.data[sample(1:161,100), c(1,3:10,12,13)]**

What does second line of code means??? thanks

A:

In the following line of code:
my.data <- the.data[sample(1:161,100), c(1,3:10,12,13)]

The first index into my.data corresponds to the desired rows, and the second index corresponds to the desired columns.
sample(1:161,100)     <-- take 100 random rows from 1 to 161
c(1,3:10,12,13)       <-- take columns 1, 3 to 10, 12, and 13

