R/lineLocations.R

In rntq472/precisePlacement: Suite of Functions to Help Get Plot Elements Exactly Where You Want Them

##' Wrapper Function for convertUnits Focused on Identifying the Locations of
##' the Margin Lines of a Plot
##' 
##' @param side Integer giving the side of the plot to count lines from.
##' @param line Numeric vector giving margin lines one wishes to find the data
##'             coordinates of.
##' 
##' @note No attempt is made to limit the returned values to the device region.
##' 
##' @author Jasper Watson
##' 
##' @examples
##' \dontrun{
##' 
##' ## Illustrate where the lines fall when using mtext:
##' plot(1:10)
##' mtext(1:26, line = -(1:26), side = 1, col = 'blue')
##' x <- lineLocations(1, 0:(-26))
##' abline(h = x, col = 'red', lty = 2)
##' }
##' 
##' @export
##' 
##
lineLocations <- function(side, line){
    
    stopifnot(side %in% 1:4, length(side) == 1, length(line) > 0)
    
    convertUnits('line', line, 'data', side = side)
    
}