1\name{is.zero} 2\alias{is.zero} 3\alias{is.zero.matrix} 4\alias{is.zero.vglm} 5\title{Zero Constraint Matrices} 6\description{ 7 Returns a logical vector from a test of whether an object such 8 as a matrix or VGLM object 9 corresponds to a 'zero' assumption. 10 11} 12\usage{ 13is.zero.matrix(object, \dots) 14is.zero.vglm(object, \dots) 15} 16\arguments{ 17 \item{object}{ 18 an object such as a coefficient matrix of a \code{\link{vglm}} object, 19 or a \code{\link{vglm}} object. 20 21 } 22 \item{\dots}{ 23 additional optional arguments. 24 Currently unused. 25 26 } 27} 28\details{ 29 These functions test the effect of the \code{zero} argument 30 on a \code{\link{vglm}} object or the coefficient matrix 31 of a \code{\link{vglm}} object. 32 The latter is obtained by \code{coef(vglmObject, matrix = TRUE)}. 33 34 35 36} 37\value{ 38 A vector of logicals, testing whether each linear/additive predictor 39 has the \code{zero} argument applied to it. 40 It is \code{TRUE} if that linear/additive predictor is 41 intercept-only, i.e., all other regression coefficients 42 are set to zero. 43 44 No checking is done for the intercept term at all, i.e., that 45 it was estimated in the first place. 46 47 48} 49\seealso{ 50 \code{\link{constraints}}, 51 \code{\link{vglm}}. 52 53 54} 55 56\examples{ 57coalminers <- transform(coalminers, Age = (age - 42) / 5) 58fit <- vglm(cbind(nBnW,nBW,BnW,BW) ~ Age, binom2.or(zero = NULL), coalminers) 59is.zero(fit) 60is.zero(coef(fit, matrix = TRUE)) 61} 62 63\keyword{models} 64\keyword{regression} 65