# model.depends

0th

Percentile

##### Identify Covariates Involved in each Model Term

Given a fitted model (of any kind), identify which of the covariates is involved in each term of the model.

Keywords
models, spatial
##### Usage
model.depends(object)
model.is.additive(object)
##### Arguments
object
A fitted model of any kind.
##### Details

The object can be a fitted model of any kind, including models of the classes lm, glm and ppm.

To be precise, object must belong to a class for which there are methods for formula, terms and model.matrix. The command model.depends determines the relationship between the original covariates (the data supplied when object was fitted) and the canonical covariates (the columns of the design matrix). It returns a logical matrix, with one row for each canonical covariate, and one column for each of the original covariates, with the i,j entry equal to TRUE if the ith canonical covariate depends on the jth original covariate.

If the model formula of object includes offset terms (see offset), then the return value of model.depends also has an attribute "offset". This is a logical value or matrix with one row for each offset term and one column for each of the original covariates, with the i,j entry equal to TRUE if the ith offset term depends on the jth original covariate.

The command model.is.additive determines whether the model is additive, in the sense that there is no canonical covariate that depends on two or more original covariates. It returns a logical value.

##### Value

• A logical value or matrix.

ppm, model.matrix

##### Aliases
• model.depends
x <- 1:10
model.is.additive(fit)