is.zero {VGAM} | R Documentation

## Zero Constraint Matrices

### Description

Returns a logical vector from a test of whether an object such as a matrix or VGLM object corresponds to a 'zero' assumption.

### Usage

    is.zero.matrix(object, ...)
    is.zero.vglm(object, ...)

### Arguments

`object` | an object such as a coefficient matrix of a `vglm` object, or a `vglm` object.
`...` | additional optional arguments. Currently unused.

### Details

These functions test the effect of the `zero` argument on a `vglm` object or the coefficient matrix of a `vglm` object. The latter is obtained by `coef(vglmObject, matrix = TRUE)`.

### Value

A vector of logicals, testing whether each linear/additive predictor has the `zero` argument applied to it. It is `TRUE` if that linear/additive predictor is intercept-only, i.e., all other regression coefficients are set to zero.

No checking is done for the intercept term at all, i.e., that it was estimated in the first place.

### See Also

`constraints`, `vglm`.

### Examples

    coalminers <- transform(coalminers, Age = (age - 42) / 5)
    fit <- vglm(cbind(nBnW,nBW,BnW,BW) ~ Age, binom2.or(zero = NULL), coalminers)
    is.zero(fit)
    is.zero(coef(fit, matrix = TRUE))

[Package VGAM version 1.0-3 Index]