Description Usage Arguments Details Value Author(s) Examples
Support functions to assist with drawing of vectors (arrows) on
ordination plots. ordiArrowMul
finds the multiplier for the
coordinates of the head of the vector such that they occupy
fill
proportion of the plot region. ordiArrowTextXY
finds coordinates for the locations of labels
to be drawn just
beyond the head of the vector.
1 2 3 4  ordiArrowTextXY(x, labels, display, choices = c(1,2),
rescale = TRUE, fill = 0.75, at = c(0,0), ...)
ordiArrowMul(x, at = c(0,0), fill = 0.75,
display, choices = c(1,2), ...)

x 
An R object, from which 
labels 
Change plotting labels. A character vector of labels for
which label coordinates are sought. If not supplied, these will be
determined from the row names of 
display 
a character string known to 
choices 
Axes to be plotted. 
rescale 
logical; should the coordinates in or extracted from

fill 
numeric; the proportion of the plot to fill by the span of the arrows. 
at 
The origin of fitted arrows in the plot. If you plot arrows
in other places than origin, you probably have to specify

... 
Parameters passed to 
ordiArrowMul
finds a multiplier to scale a bunch of
arrows to fill an ordination plot, and ordiArrowTextXY
finds
the coordinates for labels of these arrows. NB.,
ordiArrowTextXY
does not draw labels; it simply returns
coordinates at which the labels should be drawn for use with another
function, such as text
.
For ordiArrowTextXY
, a 2column matrix of coordinates for the
label centres in the coordinate system of the currently active
plotting device.
For ordiArrowMul
, a length1 vector containing the scaling
factor.
Jari Oksanen, with modifications by Gavin L. Simpson
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  ## Scale arrows by hand to fill 80% of the plot
## Biplot arrows by hand
data(varespec, varechem)
ord < cca(varespec ~ Al + P + K, varechem)
plot(ord, display = c("species","sites"))
## biplot scores
bip < scores(ord, choices = 1:2, display = "bp")
## scaling factor for arrows to fill 80% of plot
(mul < ordiArrowMul(bip, fill = 0.8))
bip.scl < bip * mul # Scale the biplot scores
labs < rownames(bip) # Arrow labels
## calculate coordinate of labels for arrows
(bip.lab < ordiArrowTextXY(bip.scl, rescale = FALSE, labels = labs))
## draw arrows and text labels
arrows(0, 0, bip.scl[,1], bip.scl[,2], length = 0.1)
text(bip.lab, labels = labs)
## Handling of ordination objects directly
mul2 < ordiArrowMul(ord, display = "bp", fill = 0.8)
stopifnot(all.equal(mul, mul2))

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