e>, if
supplied.</p><ol><li><p>The pressure data are despiked with a smooth() filter with method "3R".
This removes wild spikes that arise from poor instrument connections, etc.</p></li>
<li><p><em>Step 2.</em> If no <code>parameters</code> are given, then any data with negative pressures
are deleted.  If there is a parameter named <code>pmin</code>, then that pressure (in decibars)
is used instead as the lower limit. This is a commonly-used setup, e.g.
<code>ctdTrim(ctd, parameters=list(pmin=1))</code> rem