title: Can transparency be used with PostScript/EPS?
body: <p>I am trying to save an R plot as an EPS file but I have a problem with the following component of the plot - the gray transparent polygon (transparent black = gray effect):</p>
  
  <pre><code>polygon(x.polygon, y.polygon.6, col="#00000022", border=NA)
  </code></pre>
  
  <p>This line of code works fine when saving the plot as PDF but not as EPS. Looks like EPS does not support transparency? What other choice would I have?</p>
  
  <p>Here is the code for the full plot:</p>
  
  <pre><code>postscript(file="Figure.eps", width=5.5, height=5.5, onefile=F, horizontal=F)
  
  ts(t(data.frame(initial_timepoint, second_timepoint, third_timepoint, final_timepoint)))-&gt;obj
  obj[,-c(3,7)]-&gt;obj1
  plot(obj1, plot.type="single", lwd=0.6, xaxs="i",yaxs="i",xlab="",ylab="LV ejection fraction (%)",xaxt='n',yaxt='n',ylim=c(0,70),col="black")
  axis(1, at=c(1,2,3,4), labels=c("1","2","3","4"),cex.axis=1)
  axis(2, at=seq(0,70,10), labels=c("0%","10%","20%","30%","40%","50%","60%","70%"),cex.axis=1, las=1)
  abline(v=c(2,3),lwd=0.6,lty=2)
  
  stderr &lt;- function(x) sqrt(var(x,na.rm=TRUE)/length(na.omit(x)))
  avg&lt;-c(mean(initial_timepoint,na.rm=T), mean(second_timepoint,na.rm=T), mean(third_timepoint,na.rm=T), mean(final_timepoint,na.rm=T))
  err&lt;-c(stderr(initial_timepoint), stderr(second_timepoint), stderr(third_timepoint), stderr(final_timepoint))
  
  my.count &lt;- c(1,2,3,4)
  my.count.rev &lt;- c(4,3,2,1)
  y.polygon.6 &lt;- c((avg+err*1.96)[my.count],(avg-err*1.96)[my.count.rev])
  x.polygon &lt;- c(my.count, my.count.rev)
  polygon(x.polygon, y.polygon.6, col="#00000022", border=NA)
  lines(avg,col="black",lwd=0.8,lty=3)
  lines((avg+err*1.96),lwd=0.8,lty=3)
  lines((avg-err*1.96),lwd=0.8,lty=3)
  
  dev.off()
  </code></pre>