se.contrast(object, ...) se.contrast.aov(x, contrast.obj, coef = contr.helmert(ncol(contrast))[, 1], data = NULL) se.contrast.aovlist(...)
object
|
A suitable fit, usually from aov .
|
contrast.obj
|
The contrasts for which standard errors are
requested. This can be specified via a list or via a matrix. A single
contrast can be specified by a list of logical vectors giving the
cells to be contrasted. Multiple contrasts should be specified by a
matrix as returned by contrasts .
|
coef
|
Used when {contrast.obj} is a list; it should be a
vector of the same length as the list with zero sum. The default
value is the first Helmert contrast, which contrasts the first and
second cell means specified by the list.
|
data
|
The data frame used to evaluate contrast.obj .
|
aov
object.se.contrast
than compute directly with the coefficients.
In multistratum models, the contrasts can appear in more than one stratum; the contrast and standard error are computed in the lowest stratum and adjusted for efficiencies and comparisons between strata.
## From Venables and Ripley (1997) p.210. N <- c(0,1,0,1,1,1,0,0,0,1,1,0,1,1,0,0,1,0,1,0,1,1,0,0) P <- c(1,1,0,0,0,1,0,1,1,1,0,0,0,1,0,1,1,0,0,1,0,1,1,0) K <- c(1,0,0,1,0,1,1,0,0,1,0,1,0,1,1,0,0,0,1,1,1,0,1,0) yield <- c(49.5,62.8,46.8,57.0,59.8,58.5,55.5,56.0,62.8,55.8,69.5, 55.0, 62.0,48.8,45.5,44.2,52.0,51.5,49.8,48.8,57.2,59.0,53.2,56.0) npk <- data.frame(block=gl(6,4), N=factor(N), P=factor(P), K=factor(K), yield=yield) options(contrasts=c("contr.treatment", "contr.poly")) npk.aov1 <- aov(yield ~ block + N + K, npk) se.contrast(npk.aov1, list(N=="0", N=="1"), data=npk)