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Coef.qrrvglm(object, varlvI = FALSE, reference = NULL, ...)
"qrrvglm"
."Coef.qrrvglm"
(see Coef.qrrvglm-class
).ITolerances=TRUE
or EqualTolerances=TRUE
(and its
estimated tolerance matrix is positive-definite) then all species'
tolerances are unity by transformation or by definition, and the spread
of the site scores can be compared to them. Vice versa, if one wishes
to compare the tolerances with the sites score variability then setting
varlvI=TRUE
is more appropriate. For rank-2 QRR-VGLMs, one of the species can be chosen so that the
angle of its major axis and minor axis is zero, i.e., parallel to
the ordination axes. This means the effect on the latent vars is
independent on that species, and that its tolerance matrix is diagonal.
The argument reference
allows one to choose which is the reference
species, which must have a positive-definite tolerance matrix, i.e.,
is bell-shaped. If reference
is not specified, then the code will
try to choose some reference species starting from the first species.
Although the reference
argument could possibly be offered as
an option when fitting the model, it is currently available after
fitting the model, e.g., in the functions Coef.qrrvglm
and
lvplot.qrrvglm
.
Yee, T. W. (2006) Constrained additive ordination. Ecology, 87, 203--213.
cqo
,
Coef.qrrvglm-class
,
print.Coef.qrrvglm
,
lvplot.qrrvglm
.set.seed(123)
x2 = rnorm(n <- 100)
x3 = rnorm(n)
x4 = rnorm(n)
lv1 = 0 + x3 - 2*x4
lambda1 = exp(3 - 0.5 * (lv1-0)^2)
lambda2 = exp(2 - 0.5 * (lv1-1)^2)
lambda3 = exp(2 - 0.5 * ((lv1+4)/2)^2) # Unequal tolerances
y1 = rpois(n, lambda1)
y2 = rpois(n, lambda2)
y3 = rpois(n, lambda3)
set.seed(111)
p1 = cqo(cbind(y1,y2,y3) ~ x2 + x3 + x4, poissonff, trace=FALSE)
lvplot(p1, y=TRUE, lcol=1:3, pch=1:3, pcol=1:3)
Coef(p1)
print(Coef(p1), digits=3)
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