adding a scale

Not to bad hint :p

So From this one, I modified the function to get it work correctly: 

#############################################################################################################################################################################
####                                                            		         Scale				                                                                     ####
#############################################################################################################################################################################

scalebar <- function(loc,length,unit="km" ,degrees = TRUE,cex=par("cex"), ...) { 
	if(missing(loc)) stop("loc is missing") 
	if(missing(length)) stop("length is missing") 
	z <- c(0,length/c(4,2,4/3,1),length*1.1)+loc[1] 
	if(degrees == TRUE) length<-180*(acos((cos(length/6371)-sin(loc[2]*pi/180)*sin(loc[2]*pi/180))/(cos(loc[2]*pi/180)*cos(loc[2]*pi/180))))/pi
	x <- c(0,length/c(4,2,4/3,1),length*1.1)+loc[1] 
	y <- c(0,length/(10*3:1))+loc[2] 
	cols <- rep(c("black","white"),2) 
	for (i in 1:4) rect(x[i],y[1],x[i+1],y[2],col=cols[i])
	 for (i in 1:5) segments(x[i],y[2],x[i],y[3]) 
	 labels <- z[c(1,3)]-loc[1]
labels <- append(labels,paste(z[5]-loc[1],unit)) 
text(x[c(1,3,5)],y[4],labels=labels,cex,pos=3,offset=0) }

and pushed it in my package https://github.com/giby/Linarius if someone wanna try. I could do some improve to support other units, I'll do that latter on.  

Thanks a lot for help 

Benjamin

adding a scale

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