Add Text or Points to Ordination Plots

Description

The function adds text or points to ordination plots. Text will be used if this can be done without overwriting other text labels, and points will be used otherwise. The function can help in reducing clutter in ordination graphics, but manual editing may still be necessary.

Usage

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orditorp(x, display, labels, choices = c(1, 2), priority,
    select, cex = 0.7, pcex, col = par("col"), pcol,
    pch = par("pch"), air = 1, ...)

Arguments

x

A result object from ordination or an ordiplot result.

display

Items to be displayed in the plot. Only one alternative is allowed. Typically this is "sites" or "species".

labels

Optional text used for labels. Row names will be used if this is missing.

choices

Axes shown.

priority

Text will be used for items with higher priority if labels overlap. This should be vector of the same length as the number of items plotted.

select

Items to be displayed. This can either be a logical vector which is TRUE for displayed items or a vector of indices of displayed items. If a logical vector is used, it must have the same length as the scores plotted.

cex, pcex

Text and point sizes, see plot.default..

col, pcol

Text and point colours, see plot.default.

pch

Plotting character, see points.

air

Amount of empty space between text labels. Values <1 allow overlapping text.

...

Other arguments to scores (and its various methods), text and points.

Details

Function orditorp will add either text or points to an existing plot. The items with high priority will be added first and text will be used if this can be done without overwriting previous labels,and points will be used otherwise. If priority is missing, labels will be added from the outskirts to the centre. Function orditorp can be used with most ordination results, or plotting results from ordiplot or ordination plot functions (plot.cca, plot.decorana, plot.metaMDS).

Arguments can be passed to the relevant scores method for the ordination object (x) being drawn. See the relevant scores help page for arguments that can be used.

Value

The function returns invisibly a logical vector where TRUE means that item was labelled with text and FALSE means that it was marked with a point. The returned vector can be used as the select argument in ordination text and points functions.

Author(s)

Jari Oksanen

Examples

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## A cluttered ordination plot :
data(BCI)
mod <- cca(BCI)
plot(mod, dis="sp", type="t")
# Now with orditorp and abbreviated species names
cnam <- make.cepnames(names(BCI))
plot(mod, dis="sp", type="n")
stems <- colSums(BCI)
orditorp(mod, "sp", label = cnam, priority=stems, pch="+", pcol="grey")

## show select in action
set.seed(1)
take <- sample(ncol(BCI), 50)
plot(mod, dis="sp", type="n")
stems <- colSums(BCI)
orditorp(mod, "sp", label = cnam, priority=stems, select = take,
         pch="+", pcol="grey")

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