y useful for quarterly data. This syntax mirrors the behavior of the <code><a href="https://rdrr.io/r/stats/lag.html" class="external-link">lag()</a></code> function in R.</li>
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<strong>First differences</strong>: The first difference, e.g., <code>C_s - C_s[-1]</code>, can be written as <code>d(C_s)</code>. This is equivalent to the <code><a href="https://rdrr.io/r/base/diff.html" class="external-link">diff()</a></code> function in R. Note that this operation is defined only for the first difference; hi