R/image_scale.R

In ERottler/alptempr: Statistical analysis of alpine climatological data

#' Color scale for  image plot.
#'
#' Plot color scale of image plot.
#'
#' @param z Input data matrix. Results of moving average analysis.
#' @param zlim Maximum and minimum values.
#' @param col Vector of colors for z-value.
#' @param breaks Color breaks in z-range.
#' @param horiz Orientation of image scale
#' @param ylim ...
#' @param xlim ...
#' @return Scale for image plot.

#' @export
#'
image_scale <- function(z, zlim, col = heat.colors(12), breaks, horiz=TRUE, ylim=NULL, xlim=NULL, ...){
if(!missing(breaks)){
  if(length(breaks) != (length(col)+1)){stop("must have one more break than colour")}
}
if(missing(breaks) & !missing(zlim)){
  breaks <- seq(zlim[1], zlim[2], length.out=(length(col)+1))
}
if(missing(breaks) & missing(zlim)){
  zlim <- range(z, na.rm=TRUE)
  zlim[2] <- zlim[2]+c(zlim[2]-zlim[1])*(1E-3)#adds a bit to the range in both directions
  zlim[1] <- zlim[1]-c(zlim[2]-zlim[1])*(1E-3)
  breaks <- seq(zlim[1], zlim[2], length.out=(length(col)+1))
}
poly <- vector(mode="list", length(col))
for(i in seq(poly)){
  poly[[i]] <- c(breaks[i], breaks[i+1], breaks[i+1], breaks[i])
}
xaxt <- ifelse(horiz, "s", "n")
yaxt <- ifelse(horiz, "n", "s")
if(horiz){YLIM<-c(0,1); XLIM<-range(breaks)}
if(!horiz){YLIM<-range(breaks); XLIM<-c(0,1)}
if(missing(xlim)) xlim=XLIM
if(missing(ylim)) ylim=YLIM
plot(1,1,t="n",ylim=ylim, xlim=xlim, xaxt=xaxt, yaxt=yaxt, xaxs="i", yaxs="i", ...)
for(i in seq(poly)){
  if(horiz){
    polygon(poly[[i]], c(0,0,1,1), col=col[i], border=NA)
  }
  if(!horiz){
    polygon(c(0,0,1,1), poly[[i]], col=col[i], border=NA)
  }
}
}