Feature Request: Equation Parsing Attributes

Hey Rich,

I think Assisi would benefit from exposing some additional attributes to the equation parser:

CR/HCB – Crown ratio or height to crown base

CCF – Crown Competition Factor

CCFL – CCF in larger trees, by diameter, with the same stand

PCCFL – CCF in larger trees, by diameter, within the same plot

H5 – Average height of the 5 largest trees/acre in the stand, by diameter

D5 – Average diameter of the 5 largest trees/acre in the stand, by diameter

SDI – Stand Density Index

MaxSDI – Calibration-specific maximum SDI for a species

I've been working on some inventories in Southern Oregon and these attributes are necessary for some of the more recently published equations.