rn.</span>

<span class="sd">    :param  series:                   Prices to calculate the log returns on</span>
<span class="sd">    :type   series:                   np.array</span>

<span class="sd">    :param  lag:                      The lag between the series (in days)</span>
<span class="sd">    :type   lag:                      int</span>

<span class="sd">    :return:                          The series of log returns</span>
<span class="sd">    :rtype:                           np.array</span>
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