title: How to assign dates on x-axis to the barplot in R?
body: <p>I have multiple dates data set that I would like to plot using barplot functions in R. The data is for two different periods so I want to have its respective dates on the x-axis for ease of comparison. Here is my code so far. A_Date is for dataset in A while B_Date is for dataset contain in B.</p>
  
  <pre><code>A= runif(24, min = 25, max = 45)
  B=runif(24, min = 35, max = 100)
  DF=rbind(A,B)
  
  A_Date= as.data.frame(seq(as.Date("1987-01-01"), to= as.Date("1988-12-31"),by="months"))
  names(A_Date)= "Dates"
  A_Date$year=as.numeric(format(A_Date$Dates, "%Y"))
  A_Date$month=as.numeric(format(A_Date$Dates, "%m"))
  A_Date=A_Date[,-1]
  A_Date = as.character(paste(month.abb[A_Date$month], A_Date$year, sep = "_" ))
  
  B_Date= as.data.frame(seq(as.Date("2010-01-01"), to= as.Date("2011-12-31"),by="months"))
  names(B_Date)= "Dates"
  B_Date$year=as.numeric(format(B_Date$Dates, "%Y"))
  B_Date$month=as.numeric(format(B_Date$Dates, "%m"))
  B_Date=B_Date[,-1]
  B_Date = as.character(paste(month.abb[B_Date$month], B_Date$year, sep = "_" ))
  
  barplot(DF, beside = T, col = c("red","darkblue"), legend.text =c("1987-88", "2010-11"), args.legend =list(x="topleft", cex = 1.2, bty="n", x.intersp=0.2),
          ylab = "Precipitation (mm)", cex.axis = 1.2, cex.lab=1.5)
  </code></pre>
  
  <p>Also, I would like to have x-axis line (just like the line on y-axis. 
  Thank you</p>