# File          albers.legend
# Date          Sept. 19, 1993
#               March 9, 2005 
#                   format breaks and left align
#               Oct 31, 2006:  R version, add palette argument
#
# By              Dan Carr
#                   change underscore to arrows 
#
# Purpose       Function to produce the legend for my albers
#			  hexagon mosaic map of the U.S.                
#
 
albers.legend = function(percents,breaks,palette,brk.rnd=1){

#  Constants to shift the legend_______________________

leg.x.cen = 2.21   #2.18
leg.x.dx =   .05
leg.x.fact = 1.6
leg.ltext = leg.x.cen-leg.x.dx-.04  #2.11
leg.rtext = leg.x.cen+leg.x.dx+.04  #2.48

leg.y.min = .30
leg.y.max = 2.08    #2.1
leg.y.dy  =  .075

#  Calculated Values_________________________________

leg.y.r = leg.y.max-leg.y.min
if(!missing(percents)){
   leg.polyy = leg.y.min + leg.y.r*c(0,percents,100)/100
}else{
   leg.polyy = leg.y.min + leg.y.r*
           (breaks-min(breaks))/(max(breaks)-min(breaks))
}

leg.px = leg.x.cen + 
         c(-leg.x.dx,leg.x.dx,leg.x.dx,-leg.x.dx)

npolyy = length(leg.polyy)
ncells = npolyy-1

#  Plot rectangles____________________________________
#  Comment:  The for loop can be avoided

for (i in 1:ncells){
   leg.py = c(rep(leg.polyy[i],2),rep(leg.polyy[i+1],2))
   polygon(leg.px,leg.py,col=palette[i])
   polygon(leg.px,leg.py,density=0,col=9)
}

#  Plot line segments________________________________

  nsegs = ncells-1
# x.seg = leg.x.cen + leg.x.fact*c(-leg.x.dx,leg.x.dx)
# leg.x.seg = rep(c(x.seg,NA),nsegs)
# leg.y.seg = rep(leg.polyy[2:ncells],rep(3,nsegs))
# lines(leg.x.seg,leg.y.seg,col=1)

#  Plot Percents and Class Breaks_____________________

par(cex=.9)
if(!missing(percents))
   text(rep(leg.ltext,nsegs),
        leg.polyy[2:ncells],
        paste(percents,'%',sep=''),adj=1)
text(rep(leg.rtext,nsegs),
     leg.polyy[2:ncells],
     format(round(breaks[2:ncells],brk.rnd)),adj=0)

#  Plot Max and Min ____________________________________

text(leg.x.cen,leg.polyy[npolyy]+leg.y.dy+.02,
      paste('Max',round(breaks[npolyy],brk.rnd),sep='='),
      adj=.5)

text(leg.x.cen,leg.polyy[1]-leg.y.dy,
     paste('Min',round(breaks[1],brk.rnd),sep='='),
     adj=.5)

"finished: albers.legend"

}