title: multiple barplots in same graph maintain the same axes and same bar width
body: <p>Very stupid question but I can't find the answer online:</p>
  
  <p>Need to plot multiple barplots together like this:</p>
  
  <pre><code> i=1:4
   main = paste ("Location ", i)
  
   windows()
   par(mfrow=c(2,2))
   a&lt;-table(c(rep(10, 6), rep(4, 32)))
   b&lt;-table(c(rep(9, 6), rep(10, 32), rep(11,4)))
   c&lt;-table(c(rep(10, 6)))
   d&lt;-table(c(rep(10, 3), rep(9, 3), rep(8, 5)))
  
   barplot(a,  main=main[1], xlab='RSSI')
   barplot(b,  main=main[2], xlab='RSSI')
   barplot(c,  main=main[3], xlab='RSSI')#, width=0.5
   barplot(d,  main=main[4], xlab='RSSI')
  </code></pre>
  
  <p>1) is it possible to maintain constant the axes scale, so that it is the same on every graph?</p>
  
  <p>2) is it possible to maintain constant the bar width in the graphs? I tried with width but it does not seem to work and i would like to have it constant and fixed between graphs.</p>
  
  <p>Thanks</p>
  
  <p>EDIT: for 2) I know you can add zeros, so that all the graphics have the same number of classes involved, but since I am plotting in a for loop that I have removed to make the example simpler, I would rather use another way to do it, if it is possible.
  Thanks again</p>