Matrix Notation Exercises
Exercises

In R we have vectors and matrices. You can create your own vectors with the function c.
c(1,5,3,4)
They are also the output of many functions such as:
rnorm(10)
You can turn vectors into matrices using functions such as rbind, cbind or matrix.
Create the matrix from the vector 1:1000 like this:
X = matrix(1:1000,100,10)
What is the entry in row 25, column 3?

Using the function cbind, create a 10 x 5 matrix with first column
x=1:10
. Then add2*x
,3*x
,4*x
and5*x
to columns 2 through 5. What is the sum of the elements of the 7th row? 
Which of the following creates a matrix with multiples of 3 in the third column?
 A)
matrix(1:60,20,3)
 B)
matrix(1:60,20,3,byrow=TRUE)
 C)
x=11:20; rbind(x,2*x,3*x)
 D)
x=1:40; matrix(3*x,20,2)
 A)