Back to back histogram. Source code.
>urte2012=c(8,11,12,13,12,13,14,13,15,15,16,15,13,12,11,10,9,8,7,10,12,14,17,18,20,21,18,17,17,15)
>urte2013=c(16,12,11,10,10,9,12,16,18,20,22,18,17,18,19,17,13,15,16,18,14,12,13,18,19,21,23,20,21,22)
> tarteak=c(6,10,14,18,22,26)
> png("ondoko_histogramak_001.png")
>histo=histbackback(urte2012,urte2013,probability=F,main="Tenperatura minimoak",brks=tarteak,xlab=c("2012 urtea","2013 urtea"),axes=F)
> axis(1,at=seq(-12,12,by=2),labels=c(12,10,8,6,4,2,0,2,4,6,8,10,12))
>axis(2,at=c(0,1,2,3,4,5),labels=c(6,10,14,18,22,26),las=1,ylab="Tenperaturak")
> mtext("Tenperatura",side=2,at=3,line=2.4)
> mtext(c("Maiztasunak (2012)", "Maiztasunak (2013)"), side=1, at=c(-8, 8), line=3)
>barplot(-histo$left,col=c("navajowhite"),horiz=TRUE,space=0,add=TRUE,axes=FALSE)
>barplot(histo$right,col=c("cyan"),horiz=TRUE,space=0,add=TRUE,axes=FALSE)
> dev.off()