Question

which of the following commands will retrieve the second column from the following matrix and store in the result subj2?
data = 120, 118, 123, 122, 120, 124, 123, 119, 124
subj2 = data(1:2);
subj2 = data(2, 2);
subj2 = data(1:end, 2);
subj2 = data(2, :);
clear my selection

Explanation:

Step1: Analyze matrix indexing

In matrix indexing, if we have a matrix Data, Data(1:end, 2) means all rows (from the first row to the last row, denoted by 1:end) and the second column.

Step2: Check each option

• subj2 = Data(1:2): This is incorrect as it tries to index without specifying columns properly in a way that doesn't target the second column.
• subj2 = Data(2, 2): This only retrieves the element at the second row and second column, not the whole second column.
• subj2 = Data(2, :): This retrieves the second row, not the second column.
• subj2 = Data(1:end, 2): This correctly retrieves all elements (from the first to the last row) of the second column.

Answer:

subj2 = Data(1:end, 2) (the option that is selected in the image) is the correct command.