 In the <code>nb2listw</code>function, it is also
possible to pass through general weights, such as inverse distances,
shares of boundary lengths and so on.</p>
<p>The third component of a <code>listw</code> object records the
<code>style</code> of the weights as a character code, with
<code>"B"</code> for binary weights taking values zero or one (only one
is recorded), <code>"W"</code> for row-standardised weights, and so on.
In order to subset <code>listw</code> objects, knowledge of the
<code>style</code