# Making Matrices 2

• If the elements within a row of a large matrix (e.g. 10-by-10) follow a sequence, the colon operator `:` would be useful.
• For example, specifying the elements of a matrix like this, `[1:10]` creates a row matrix with 10 elements ascending from 1 to 10. The default increment is 1. In order specify a different incremental value another value is added so that `[4:2:14]` creates a row matrix with elements 4, 6, 8, 10, 12 and 14 in that order. EXERCISE 1

Try and determine the matrix the codes below would generate. Write them down and then run the code to see if you were right!

1. `A = eye(7)`
2. `B = [ 7:12 ]`
3. `C = [ 0:2:10, 10:4:30]`
4. `E = [ -pi : pi/4 : pi ]` (NB: pi = π)
5. `J = ones(2,5)`

MISCELLANEOUS EXERCISE:

By hand, try and construct a 3-by-3 matrix using the numbers 1 to 9 in which all the elements in each column and row add up to the same thing. If found that easy, repeat the procedure for a 4-by-4 matrix using 1 to 16.

There’s a way to generate this on MATLAB. (Hint: It is magical.)

(For more on making matrices and special matrices, follow the links: Array Creation and Special Matrices.)