R: Parse Trellis formula

G_latticeParseFormula {lattice}

R Documentation

Parse Trellis formula

Description

this function is used by high level Lattice functions like xyplot to parse the formula argument and evaluate various components of the data.

Usage

latticeParseFormula(model, data, dimension = 2,
                    subset = TRUE, groups = NULL,
                    multiple, outer,
                    subscripts,
                    drop)

Arguments

`model`	the model/formula to be parsed. This can be in either of two possible forms, one for 2d and one for 3d formulas, determined by the `dimension` argument. The 2d formulas are of the form `y ~ x\| g1 * ... gn`, and the 3d formulas are of the form `z ~ x y \| g1 * ...* gn`. In the first form, `y` may be omitted. The conditioning variables `g1, ...,gn` can be omitted in either case.
`data`	the environment/dataset where the variables in the formula are evaluated.
`dimension`	dimension of the model, see above
`subset`	index for choosing a subset of the data frame
`groups`	the grouping variable, if present
`multiple`, `outer`	logicals, determining how a ‘+’ in the y and x components of the formula are processed. See `xyplot` for details
`subscripts`	logical, whether subscripts are to be calculated
`drop`	logical or list, similar to the `drop.unused.levels` argument in `xyplot`, indicating whether unused levels of conditioning factors and data variables that are factors are to be dropped.

Value

returns a list with several components, including left, right, left.name, right.name, condition for 2-D, and left, right.x, right.y, left.name, right.x.name, right.y.name, condition for 3-D. Other possible components are groups, subscr

Author(s)