makeAdditiveFormula
Construct modeling formulae programatically
Description
Given the names of the predictor and response variables, construct a formula suitable for use with modeling functions like lm and glm.
Usage
makeAdditiveFormula(predictors, responses, env = parent.frame(),
onMultipleResponse = "cbind", emptyResponsesOutput = stop("no response"))
Arguments
| predictors |
A character vector listing the names of the predictor variables or a list
of expressions to use as the predictor variables.
|
| responses |
A character vector listing the names of the response variables or a list
of expressions to use as the response variables.
|
| env |
In R, the environment attribute of the returned formula will be set to this environment.
Names in the formula not otherwise found will be searched for in this environment.
In S+, which has no concept of an environment, this is not used.
|
| onMultipleResponse |
A character string, either "cbind" or "+".
If there are multiple responses should they be tied together by a call to "cbind"
(the common thing in modeling functions) or by calls to "+" (uncommon, but used
in ftable)?
|
| emptyResponsesOutput |
If there are no response variables (or expressions) listed, use this as a placeholder.
The default action is to signal an error. You can supply NULL to mean that not
having a response is acceptable.
|
Details
The most common usage is just makeAdditiveFormula(predictors, responses) where
predictors and responses list the names of variables.
makeAdditiveFormula calls the two helper routines .makeAdditiveExpr
and .makeCbindExpr to build the formula and it is possible that one might
want to use them directly to construct unusual formulae.
Value
If there is only one response variable makeAdditiveFormula returns a formula of the form
Response ~ Predictor1 + Predictor2 + ...; if there is more than one response variable it returns
either cbind(Response1,Response2,...) ~ Predictor1 + Predictor2 + ...
or Response1 + Response2 + ... ~ Predictor1 + Predictor2 + ..., depending on the
value of onMultipleResponses.
See Also
Examples
makeAdditiveFormula(predictors=c("Age", "Sex"), responses=c("Attitude"))
makeAdditiveFormula(predictors=c("Town"), responses=c("NumCases", "Population"))