martinEk: Martin and Ek 1984

In johngodlee/compInd: Forest tree-tree competition indices

Martin and Ek 1984

Description

Martin and Ek 1984

Usage

martinEk(dbh, dist, focal_dbh)

Arguments

dbh	vector of DBH (diameter at breast height) measurements of competitor trees
dist	vector of distances from focal tree to competitor trees
focal_dbh	DBH of focal tree

Details

Gives the sum of ratios of competitor to focal tree DBHs, multiplied by the exponential of distances divided by competitor DBH plus focal DBH. Given by the equation:

\sum_{j\neq{}i}^{n} (d_{j} / d_{i}) exp((16l_{ij}) / (d_{i} + d_{j}))

Value

value of competition index for focal tree

References

Martin G. L., Ek A. R. (1984). A Comparison of Competition Measures and Growth Models for Predicting Plantation Red Pine Diameter and Height Growth. Forest Science. Volume 30. Pages 731-743.

Examples

data(bicuar)
nb <- nearNeighb(bicuar$x, bicuar$y, bicuar$stem_id, k = 4) 
lapply(nb, function(x) {
  nb <- merge(x, bicuar, by.x = "nb", by.y = "stem_id")
  focal_diam <- unique(bicuar[bicuar$stem_id == nb$focal,"diam"])
  martinEk(nb$diam, nb$nb_dist, focal_diam)
  })

johngodlee/compInd documentation built on Aug. 5, 2024, 8:44 a.m.