merge_taxa | R Documentation |
The function offers a simple way to merge taxa with identical names in a vegetation table, e.g. due to necessary harmonization of the taxon level, to combine taxa of different layers or to remove duplicates. The original cover-abundance scales are maintained.
merge_taxa(
vegtable,
scale = "percentage",
layers = "FALSE",
method = "independent",
clean_matrix = FALSE,
backtransform = TRUE
)
vegtable |
Data frame with samples in columns and taxa in rows. Taxon names must be in the first column. |
scale |
Cover-abundance scale(s) of data. Default is percentage cover (values between 0 and 100) ( |
layers |
A logical evaluation to |
method |
Choice of method to combine cover. |
clean_matrix |
A logical evaluation to |
backtransform |
A logical evaluation to |
A data frame based on vegtable
with merged taxa.
The format required for this function is a data frame with samples in columns and taxa in rows, which corresponds to the export format of vegetation tables from Turboveg (Hennekens & Schaminee 2001). Taxon names must be in the first column of the table (not row names as these do not allow duplicates). If vegetation layers are to be included, layer information must be stored in the second column of the table. Taxa will then be merged only within the defined layers.
If a cover-abundance scale from scale_tabs
is defined, all cover-abundance values will be transformed into percentage cover for the merging process, and then back-transformed into the original cover-abundance scale.
When combining cover values there are two possibilities following Fischer (2014) and Tichý & Holt (2011).
method = "independent"
(default) assumes that covers can overlap and that they do so independently of each other (e.g. individuals of the lower layer are growing beneath individuals of the upper layer).
In case of two layers the sum of the cover of layer 1 and layer 2 is the sum of the covers minus the overlap. ($p1 + p2- p1 * p2)
Usually the choice when merging the same taxon from different (sub-)layers.
method = "exclusive"
assumes the covers are mutually exclusive, cover values will be simply summed up (e.g. individuals grow side by side).
Usually the chouce when merging within layers, e.g. aggregating distinct taxa.
Percentage cover values will eventually be truncated to 100
You may use the function trans_matrix
to easily transpose the resulting vegetation table into a statistically analyzable species matrix.
Friedemann von Lampe (fvonlampe@uni-goettingen.de)
Fischer, H. S. (2015): On the combination of species cover values from different vegetation layers. Applied Vegetation Science, 18: 169–170. \Sexpr[results=rd]{tools:::Rd_expr_doi("https://doi.org/10.1111/avsc.12130")}
Tichý, L. & Holt, J. (2011): JUICE. Program for management, analysis and classification of ecological data. Vegetation Science Group, Masaryk University Brno, CZ.
## Merge taxa with identical names without any layer information
# Transpose table to required format
schedenveg.t <- data.frame(species = names(schedenveg), t(schedenveg))
# Add two duplicated taxa
schedenveg.t <- rbind(schedenveg.t, schedenveg.t[c(55, 61), ])
# Merge duplicated taxa using default 'independent' method
schedenveg.merged <- merge_taxa(schedenveg.t, scale = "percentage")
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