> data frame which is <code>4</code> and so our loop runs from <code>i = 1</code> to <code>i = 4 - 1</code> which is <code>i = 3</code>. We’ll come back to why we need to subtract 1 from this in a minute.</p>
<p>So in the first iteration of the loop <code>i</code> takes on the value <code>1</code>. The <code>multiply_columns()</code> function multiplies the <code>city[, 1]</code> (<code>porto</code>) and <code>city[, 1 + 1]</code> (<code>aberdeen</code>) columns and stores it in the <code>temp[[1]]</code>