check.for.columns

must.have

Stop if a data.frame does not have some columns.

The directlabels package provides an extensible framework
        for automatically placing direct labels onto multicolor lattice
        or ggplot2 plots.  It includes heuristics for examining
        "trellis" and "ggplot" objects and inferring an appropriate
        Positioning Method for placing the labels. Furthermore, the
        design of directlabels makes it simple to create Positioning
        Methods for specific plots or libraries of portable Positioning
        Methods that can be re-used.

check.for.columns: check for columns

Description

Usage

Arguments