de> and <code>"lm"</code> methods.  If <code>e=1</code>, then the
neighbourhood for the i-th pressure extends from the (<code>i-1</code>)-th pressure to
the (<code>i+1</code>)-th pressure.  At the endpoints it is assumed that the outside
bin is of the same pressure range as the first inside bin.  For other values of
<code>e</code>, the neighbourhood is expanded linearly in each direction.  If the
<code>"lm"</code> method produces warnings about "prediction from a rank-deficient
fit", a larger value of <code