fparse: Parse and exten formula input from a model and return the DV, IV, and associated terms.
Description
Formula input from e.g., lm, may be extended to include mediators, quadratic and partial terms using a standard syntax. This is use by lmCor and mediate.
Usage
fparse(expr)
Value
y
A list of elements from the left side of the formula
x
A list of elements from the right side of the formula
m
A list of those elements of the formula included in ()
prod
A list of elements separated by a * sign
ex
A list of elements marked by I()
Arguments
expr
A legitimate expression in the form y ~ x1 , etc. (see details)
Author
William Revelle
Details
The basic formula input given as DV1 + DV2 ~ IV1 + IV2 + (IV3) + I(IV4^2) - IV5 will be parsed to return 2 DVs (1 and 2), two normal IVs (1 and 2), a mediator (IV3) a quadratic (IV4) and a variable to be partialed (IV5). See the various examples in lmCor and mediate.