title: Barchart help in R
body: <p>I am trying to set up a bar chart to compare control and experimental samples taken of specific compounds. The data set is known as 'hydrocarbon3' and contains the following information:</p>
  
  <pre><code>    Exp.    Contr.
  c12 89  49
  c17 79  30
  c26 78  35
  c42 63  3
  pris    0.5 0.8
  phy 0.5 0.9
  nap 87  48
  nap1    83  44
  nap2    78  44
  nap3    73  20
  acen1   81  50
  acen2   86  46
  fluor   83  11
  fluor1  68  13
  fluor2  79  17
  dibe    65  7
  dibe1   67  6
  dibe2   56  10
  phen    82  13
  phen1   70  12
  phen2   65  15
  phen3   53  14
  fluro   62  9
  pyren   48  11
  pyren1  34  10
  pyren2  19  8
  chrys   22  3
  chrys1  21  3
  chrys2  21  3
  </code></pre>
  
  <p>When I create a bar chart with the formula: </p>
  
  <pre><code>barplot(as.matrix(hydrocarbon3),
          main=c("Fig 1. Change in concentrations of different hydrocarbon compounds\nin sediments with and without the presence of bacteria after 21 days"),
          beside=TRUE,
          xlab="Oiled sediment samples collected at 21 days",
          space=c(0,2),
          ylab="% loss in concentration relative to day 0")
  </code></pre>
  
  <p>I receive this diagram, however I need the control and experimental samples of each chemical be next to each other allow a more accurate comparison, rather than the experimental samples bunched on the left and control samples bunched on the right: Is there a way to correct this on R?  <img src="https://i.stack.imgur.com/l7y7n.jpg" alt="barchart"></p>