   b_2    b_3
1 Pinaceae  Pinus   lambertiana  2.60 -0.00726 -0.00458 -0.442
2 Ericaceae Arbutus menziesii    2.71 -0.00367 -0.00455 -0.505</code></pre></div><p></p><hr><code>rc = 1 - ((1)/(1 + exp(b_0 + b_2 * ccfl + b_3 * log(gn) + b_4 * (dsob/hst))))</code><ul><li><p><code>rc [ft ft-1]</code> - crown ratio</p></li>
<li><p><code>hst [ft]</code> - total height of the stem</p></li>
<li><p><code>ccfl [ft2 ft-2]</code> - crown competition factor of large trees</p></li>
<li><p><code>gn [ft2 acre-1]</code> - sta