cwm: Community Weighted Mean.

In BAT: Biodiversity Assessment Tools

Community Weighted Mean.

Description

Average value of each of a series of traits in multiple communities.

Usage

cwm(comm, trait, abund = TRUE, geo = FALSE, na.rm = FALSE)

Arguments

comm	A sites x species matrix, with incidence or abundance data about the species in the community.
trait	A species x traits matrix, with trait values for each species in comm.
abund	A boolean (T/F) indicating whether abundance data should be used (TRUE) or converted to incidence (FALSE) before analysis. If not specified, default is TRUE.
geo	Calculate using geometric instead of arithmetic mean (Liu et al. 2026)?
na.rm	Remove NA values before calculating cwm.

Details

Community weighted mean is used to compare communities in terms of their "typical" trait values.

Value

A sites x trait matrix with mean value per site and trait.

References

Liu, C., Yang, X. & He, N. (2026) Rethinking community-weighted means: why geometric averages matter. Oikos, in press.

Examples

comm <- matrix(c(2,5,0,0,0,1,1,0,0,0,0,1,2,0,0,0,0,0,10,1), nrow = 4, ncol = 5, byrow = TRUE)
rownames(comm) = c("Site1","Site2","Site3","Site4")
colnames(comm) = c("Sp1","Sp2","Sp3","Sp4","Sp5")
trait <- data.frame(Trait1 = c(1,0,0,2,0), Trait2 = c(rep("A",2), rep("B",3)))
rownames(trait) = colnames(comm)
cwm(comm, trait)
cwm(comm, trait, FALSE)
cwm(comm, trait, geo = TRUE)

BAT documentation built on March 30, 2026, 5:09 p.m.