R/axis_title.R

In RemkoDuursma/plover: A Collection of Convenient Plotting Functions

#' Adds an axis title in the margin
#' @description A simple wrapper for \code{\link{mtext}}, making sure that the character size is adjusted to be identical to the character size used on the ordinary axes, and respecting the setting for \code{mgp} in \code{\link{par}}. This is especially handy when plotting multiple panels (via the use of \code{par(mfrow=...)}), because axis labels are automatically adjusted in that case (see entry for \code{mfrow} in \code{\link{par}}).
#' @examples
#' # Plot a second axis
#' set.seed(1)
#' x <- rnorm(100)
#' y <- x + rnorm(100)
#' z <- rnorm(100) - x
#' 
#' o <- par(mar=c(5,5,2,5)) 
#' plot(x, y, ylab="X variable")
#' points(x, z, pch=19)
#' axis_title("Z variable", side = 4)
#' axis(4)
#' par(o)
#' @export
axis_title <- function(text, side, ...){
  
  # Get actual cex.lab, see ?par under mfrow
  mf <- par()$mfrow
  m <- 1
  if(mf[1] ==2 & mf[2] == 2)m <- 0.83
  if(max(mf) > 2)m <- 0.66
  mtext(side=side, text=text, cex=m*par()$cex.lab, line=par()$mgp[1], ...)
  
}