Matlab_02b

Matrix manipulation

Matlab stores as many values as you wish inside one variable name in either a row, or a column, or a multi-dimensional structure.

First example is a row of values:

    a = [1 2 3 4]; % the values are separated by spaces

The second example is a column of values:

    source_data = [3.22; 6.77; 8.45; 0.11; 7.02]; % separated by semicolons

And the third example contains rows and columns:

    readings = [2 3 4; 5 3 2; 3 4 5; 5 3 1];

The example above is a 4-by-3 matrix, 4 rows and 3 columns.

How many rows and how many columns are there in the variable my_readings? If there is any doubt type:

    size(readings)

This will give you the size of matrix - rows first and then columns. To see the average of each column type:

    mean(readings,1)

And to get the average of the rows type:

mean(readings,2)

Try out the following lines. What do they do?

    max(readings);

    max(readings(:));

    imagesc(readings);

    plot(readings);

    plot(readings');