R/MaxCrownWidth.R

In ryanmismith/inventoryfunctions: Forestry Inventory Functions

#' Maximum Crown Width
#'
#' This function returns the maximum crown width for an open grown tree
#' for the most common species found in the acadian forest.
#' ##
#' Metric
#' ##
#'
#'###
#' SPP included: BF, BS, EH, WP, NC, RS, WS, AB, GB, RB, RO, PB, QA, RM, SM, YB.
#' SPP that are not included can be enter as 'OH' for hardwoods and 'OS' for softwoods.
#' If no SPP is entered a standard coefficient will be used but may not reflect the
#' crown conditions accurately - please enter 'OS' or 'OH' if species is not included.
#'### MCW is a dependency needed to calculate LCW.
#'
#'@seealso [inventoryfunctions::LCW]
#'
#'@family Crown Functions
#'@param SPP Tree Species: use the FVS code
#'@param DBH Diameter at breast height in cm.
#'
#'@return This function returns an numeric vector length n providing the maximum crown width value for n trees in meters.
#'
#'@references
#'Russell, M. B., & Weiskittel, A. R. (2011). Maximum and Largest Crown Width Equations for 15 Tree Species in Maine.
#'Northern Journal of Applied Forestry, 28(2), 84–91. https://doi.org/10.1093/njaf/28.2.84

#'@examples
#'
#'MCW("BF", 25)
#'
#'SPP   <- c("BF", "RO", "RS", "YB", "RO", "YB")
#'DBH   <- c(24, 34, 18, 41, 6, 20)
#'
#'example <- mapply(MCW, SPP, DBH)
#'
#' \dontrun{
#' Tibble %>% mutate(MCW = MCW("SPP Variable", "DBH Variable"))
#' }
#'
#'@export


MCW <- function(SPP,DBH)
{
  SPcodes=c('BF','BS','EH','WP','NC','RS','WS','AB','GB','RB','RO','PB','QA',
            'RM','SM','YB','OH','OS','99')
  coefs = matrix(c(
    # a1           a2
    1.37       , 0.572      ,    # BF
    0.535      , 0.742      ,    # BS
    2.44       , 0.408      ,    # EH
    1.24       , 0.585      ,    # WP
    1.63       , 0.436      ,    # NC
    1.80       , 0.461      ,    # RS
    1.50       , 0.496      ,    # WS
    2.93       , 0.434      ,    # AB
    2.24       , 0.382      ,    # GB
    2.24       , 0.382      ,    # RB
    4.08       , 0.310      ,    # RO
    1.48       , 0.623      ,    # PB
    1.31       , 0.586      ,    # QA
    2.17       , 0.491      ,    # RM
    3.31       , 0.356      ,    # SM
    4.04       , 0.308      ,    # YB
    4.04       , 0.308      ,    # OH
    1.597128571, 0.513957143,    # OS
    2.24262    , 0.462653333),   # 99
    ncol=2,byrow=TRUE)
  sprow = match(SPP,SPcodes)
  sprow[is.na(sprow)] = length(SPcodes)
  X <- coefs[sprow,1]*DBH**coefs[sprow,2]
  return(X)
}