title: how do you create bar charts for two different data columns and one group cloumn
body: <p>my data frame:</p>
  
  <pre><code>dput(head(x,3))
  structure(list(Programs = structure(1:3, .Label = c("400.perlbench", 
  "401.bzip2", "403.gcc", "429.mcf", "445.gobmk", "456.hmmer", 
  "458.sjeng", "462.libquantum", "464.h264ref", "471.omnetpp", 
  "473.astar", "483.xalancbmk"), class = "factor"), Base_Run_Time = c(988.746037, 
  1401.357446, 821.134215), Base_Rate = c(790.49624, 550.8944, 
  784.28104), Base_Geo_Mean = c(837.6709, 837.6709, 837.6709), 
      Bench_Mark_Run_Time = c(827.236707, 1329.663649, 818.863431
      ), Peak_Rate = c(944.83232, 580.59792, 786.45592), Chip = structure(c(2L, 
      2L, 2L), .Label = c("E5_2660", "E7_4860", "ultrasparc"), class = "factor"), 
      Bench_Geo_Mean = c(790.4498, 790.4498, 790.4498), Percent_Difference = c(0.06, 
      0.06, 0.06)), .Names = c("Programs", "Base_Run_Time", "Base_Rate", 
  "Base_Geo_Mean", "Bench_Mark_Run_Time", "Peak_Rate", "Chip", 
  "Bench_Geo_Mean", "Percent_Difference"), row.names = c(NA, 3L
  ), class = "data.frame")
  </code></pre>
  
  <p>I need to create a bar chart where for each group, need to have Base_Run_Time and Bench_Mark_Run_Time side by side, one having orange and the other having blue color.</p>
  
  <p>I have tried something like this, but this gives me a stack chart. I need bar chart for each Base_Run_Time and Bench_Mark_Run_Time:</p>
  
  <pre><code>ggplot(x)+geom_bar(data=x, aes(Programs, Base_Run_Time, colour="orange", group=Chip), stat="identity") + geom_bar(data=x, aes(Programs,Bench_Mark_Run_Time, colour="blue", fill="green", group=Chip), stat="identity")
  </code></pre>
  
  <p>any ideas?</p>