findq: Find a "q" value from stand parameters
In Mensuration: Miscellaneous Forest Mensuration Routines

Description Usage Arguments Details Value Author(s) See Also Examples

This routine will simply return a “q” value for a stand from the desired basal area and number of trees in the largest class.

findq(dbh.low = 0.5,
      dbh.up = 19.5,
      dc.width = 1,
      B = 80,
      N.max = 2,
      units = c("English", "metric"),
      runQuiet = FALSE,
      ...)

`dbh.low`	The lower midpoint dbh.
`dbh.up`	The upper midpoint dbh.
`dc.width`	The DBH class width (should be integer) for all classes.
`B`	Basal area per acre/hectare.
`N.max`	Number of trees in the largest dbh class.
`units`	Measurement units (character): “English” or “metric”.
`runQuiet`	TRUE: no feedback; FALSE: some feedback.
`...`	Arguments to be passed on to `dbhClassLimits` or gobbled up.

This is very simple, and solves the well-known relation between the diminution coefficient and the stand parameters. Just pass it the diameter ranges, the basal area and number of trees in the largest class to find the “q” value.

The results can be easily corroborated with qDistnShiny; e.g., one can generate a stand table from the “q” value (to two decimal places) with qDistnShiny.

Note that if uniroot fails (this is what is used to find the “q” value), then it is probably because your input parameters do not make sense.

A list with...

`qValue`	The “q” value.
`qTable`	The stand table for this stand.

JHG.

dbhClassLimits for how the diameter classes are handled.

findq(0.5, 13.5, 1, 80, 8.0744732)$qValue       #q=1.1999988
findq(2, 18, 4, 100, 23.7)                      #q=1.199835
qv = findq(1, 23, 2, 18, 57.026315, 'metric')   #q=1.1999988
qv$qTable