Matlab_02a

Matrices

A variable that contains a single value like my_age in the earlier example is treated by Matlab as 1-by-1 matrix of numbers. This may sound like a complication but (for mathematicians and programmers at least) it turns out to make life much simpler in many ways.

A feature of Matlab is that it can calculate more than one answer in the same expression:

my_scores = [1 2 3 4 5];

my_scores = my_scores + 2;

my_scores

my_scores =

3 4 5 6 7

You can see that Matlab has added 2 to all the values inside the variable. The variable my_scores in the example above is a 1-by-5 matrix because it has 1 row and 5 columns. People sometimes call this a 'row vector' just to be confusing. I will stick to using the word 'matrix'.

Note that rounded brackets, or any other sort of bracket, will not work to enclose matrices:

(1 2 3 4 5) + 2

??? (1 2 3 4 5) + 2

       |

Error: Unexpected MATLAB expression.

Try to predict what will happen here:

[1 2 3 4 5] + [1 2 3 4 5]

and here

[1 2 3 4 5] * [1 2 3 4 5]

Were you right in both cases? Unless you have previous experience with this sort of work I doubt if you were. If you are familiar with matrix arithmetic it will all come as no surprise to you.

Note that using .* ( a multiply with a dot in front of it) does get the result you expect:

[1 2 3 4 5] .* [1 2 3 4 5]

ans =

1 4 9 16 25

There is a dotted version of divide too, try it out for yourself.