Add Arrows and Line Segments to Ordination Diagrams
Description
Functions to add arrows, line segments, regular grids of
points. The ordination diagrams can be produced by vegan
plot.cca
, plot.decorana
or
ordiplot
.
Usage
1 2 3 4 5 6  ordiarrows(ord, groups, levels, replicates, order.by, display = "sites",
col = 1, show.groups, startmark, label = FALSE, length = 0.1, ...)
ordisegments(ord, groups, levels, replicates, order.by, display = "sites",
col = 1, show.groups, label = FALSE, ...)
ordigrid(ord, levels, replicates, display = "sites", lty = c(1,1),
col = c(1,1), lwd = c(1,1), ...)

Arguments
ord 
An ordination object or an 
groups 
Factor giving the groups for which the graphical item is drawn. 
levels, replicates 
Alternatively, regular
groups can be defined with arguments 
order.by 
Order points by increasing order of this variable
within 
display 
Item to displayed. 
show.groups 
Show only given groups. This can be a vector, or

label 
Label the 
startmark 
plotting character used to mark the first item. The
default is to use no mark, and for instance, 
col 
Colour of lines, 
length 
Length of edges of the arrow head (in inches). 
lty, lwd 
Line type, line width used for

... 
Parameters passed to graphical functions such as

Details
Function ordiarrows
draws arrows
and
ordisegments
draws line segments
between
successive items in the groups. Function ordigrid
draws line
segments
both within the groups and for the
corresponding items among the groups.
Note
These functions add graphical items to ordination graph: You must draw a graph first.
Author(s)
Jari Oksanen
See Also
The functions pass parameters to basic graphical functions, and
you may wish to change the default values in arrows
,
lines
and segments
. You can pass
parameters to scores
as well.
Examples
1 2 3 4 5 6 7 8 9 10 11 12 13  example(pyrifos)
mod < rda(pyrifos)
plot(mod, type = "n")
## Annual succession by ditches, colour by dose
ordiarrows(mod, ditch, label = TRUE, col = as.numeric(dose))
legend("topright", levels(dose), lty=1, col=1:5, title="Dose")
## Show only control and highest Pyrifos treatment
plot(mod, type = "n")
ordiarrows(mod, ditch, label = TRUE,
show.groups = c("2", "3", "5", "11"))
ordiarrows(mod, ditch, label = TRUE, show = c("6", "9"),
col = 2)
legend("topright", c("Control", "Pyrifos 44"), lty = 1, col = c(1,2))
