title: trouble adding geom_vline to ggplot2
body: <p>I have a large time series data set, which I've used xts to summarize in 30 second periods. Not sure how to make this set easily reproducible but it looks like this</p>
  
  <pre><code>&gt; str(taonedf)
  'data.frame':   480 obs. of  2 variables:
   $ time : POSIXct, format: "2013-01-06 13:00:29" "2013-01-06 13:00:59" "2013-01-06 13:01:29" ...
   $ count: int  20763 12030 22188 12183 21112 11628 21543 12609 20095 12992 ...
  &gt; head(taonedf)
                   time count
  1 2013-01-06 13:00:29 20763
  2 2013-01-06 13:00:59 12030
  3 2013-01-06 13:01:29 22188
  4 2013-01-06 13:01:59 12183
  5 2013-01-06 13:02:29 21112
  6 2013-01-06 13:02:59 11628
  </code></pre>
  
  <p>I've plotted a normal line plot of this and it works fine.</p>
  
  <pre><code>ggplot(data=taonedf, aes(x=time, y=count/30)) + #
    geom_line(color="#009E73") + 
    scale_y_continuous(name="requests per second", labels = format_format(scientific=FALSE, big.mark=",")) +
    scale_x_datetime(name="",labels = date_format("%b %d\n%H:%M") ) +
    labs(title=paste("Requests per Second - All Requests",count,sep="\n")) +
    theme(legend.position = "none")
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/NXIQN.jpg" alt="enter image description here"></p>
  
  <p>I want to add some vline annotations. I've created a second dataframe called EV, it looks like this:</p>
  
  <pre><code>&gt; str(ev)
  'data.frame':   10 obs. of  2 variables:
   $ dt   : POSIXct, format: "2013-01-06 13:45:00" "2013-01-06 14:18:00" "2013-01-06 14:49:00" ...
   $ event: Factor w/ 9 levels "Event 1",..: 7 8 3 2 5 6 1 4 2 9
  
  &gt; head(ev)
                     dt                                            event
  1 2013-01-06 13:45:00                                          Event 1
  </code></pre>
  
  <p>Now, when I add the vline option I get odd results. I'm using the same date time format between the two so the scale should align. </p>
  
  <pre><code>ggplot(data=taonedf, aes(x=time, y=count/30)) + 
    geom_line(color="#009E73") + 
    geom_vline(data=ev,aes(xtintercept=dt))+
    scale_y_continuous(name="requests per second", labels = format_format(scientific=FALSE, big.mark=",")) +
    scale_x_datetime(name="",labels = date_format("%b %d\n%H:%M") ) +
    labs(title=paste("Requests per Second - All Requests",count,sep="\n")) +
    theme(legend.position = "none")
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/A58PS.jpg" alt="enter image description here"></p>
  
  <p>What am I missing? This doesn't appear to be that hard. All of the documentation and examples show simple numeric X axis so I'm assuming there is some issue with dates in the X axis but I can't pinpoint it. Any help would be appreciated.</p>
  
  <pre><code>&gt; dput(taonedf)
  structure(list(time = structure(c(1357506029.996, 1357506059.999, 
  1357506089.997, 1357506119.998, 1357506149.998, 1357506179.996, 
  1357506209.996, 1357506239.993, 1357506269.999, 1357506299.996, 
  1357506329.998, 1357506359.998, 1357506389.999, 1357506419.998, 
  1357506449.986, 1357506479.996, 1357506509.99, 1357506539.988, 
  1357506569.996, 1357506599.999, 1357506629.991, 1357506659.998, 
  1357506689.999, 1357506719.995, 1357506749.996, 1357506779.998, 
  1357506809.998, 1357506839.997, 1357506869.996, 1357506899.996, 
  1357506929.997, 1357506959.994, 1357506989.998, 1357507019.999, 
  1357507049.999, 1357507079.998, 1357507109.998, 1357507139.999, 
  1357507169.998, 1357507199.99, 1357507229.999, 1357507259.999, 
  1357507289.999, 1357507319.998, 1357507349.997, 1357507379.997, 
  1357507409.999, 1357507439.998, 1357507469.994, 1357507499.996, 
  1357507529.996, 1357507559.996, 1357507589.995, 1357507619.988, 
  1357507649.999, 1357507679.994, 1357507709.996, 1357507739.996, 
  1357507769.994, 1357507799.991, 1357507829.999, 1357507859.999, 
  1357507889.999, 1357507919.999, 1357507949.999, 1357507979.999, 
  1357508009.999, 1357508039.999, 1357508069.998, 1357508099.999, 
  1357508129.999, 1357508159.999, 1357508189.999, 1357508219.998, 
  1357508249.999, 1357508279.999, 1357508309.999, 1357508339.999, 
  1357508369.999, 1357508399.999, 1357508429.998, 1357508459.999, 
  1357508489.999, 1357508519.999, 1357508549.999, 1357508579.999, 
  1357508609.999, 1357508639.999, 1357508669.999, 1357508699.999, 
  1357508729.999, 1357508759.998, 1357508789.999, 1357508819.998, 
  1357508849.999, 1357508879.998, 1357508909.999, 1357508939.996, 
  1357508969.999, 1357508999.999, 1357509029.999, 1357509059.999, 
  1357509089.999, 1357509119.999, 1357509149.999, 1357509179.999, 
  1357509209.999, 1357509239.999, 1357509269.999, 1357509299.999, 
  1357509329.999, 1357509359.999, 1357509389.999, 1357509419.999, 
  1357509449.999, 1357509479.999, 1357509509.999, 1357509539.999, 
  1357509569.976, 1357509599.999, 1357509629.999, 1357509659.999, 
  1357509689.999, 1357509719.999, 1357509749.996, 1357509779.999, 
  1357509809.999, 1357509839.999, 1357509869.999, 1357509899.999, 
  1357509929.999, 1357509959.996, 1357509989.999, 1357510019.997, 
  1357510049.998, 1357510079.997, 1357510109.999, 1357510139.999, 
  1357510169.999, 1357510199.999, 1357510229.999, 1357510259.999, 
  1357510289.999, 1357510319.999, 1357510349.999, 1357510379.999, 
  1357510409.999, 1357510439.999, 1357510469.999, 1357510499.999, 
  1357510529.999, 1357510559.999, 1357510589.999, 1357510619.999, 
  1357510649.999, 1357510679.999, 1357510709.999, 1357510739.983, 
  1357510769.999, 1357510799.999, 1357510829.999, 1357510859.999, 
  1357510889.999, 1357510919.999, 1357510949.999, 1357510979.999, 
  1357511009.997, 1357511039.999, 1357511069.999, 1357511099.999, 
  1357511129.999, 1357511159.999, 1357511189.999, 1357511219.999, 
  1357511249.999, 1357511279.999, 1357511309.999, 1357511339.999, 
  1357511369.999, 1357511399.999, 1357511429.999, 1357511459.999, 
  1357511489.999, 1357511519.999, 1357511549.999, 1357511579.999, 
  1357511609.999, 1357511639.999, 1357511669.999, 1357511699.999, 
  1357511729.999, 1357511759.999, 1357511789.996, 1357511819.999, 
  1357511849.999, 1357511879.999, 1357511909.999, 1357511939.993, 
  1357511969.999, 1357511999.998, 1357512029.999, 1357512059.999, 
  1357512089.999, 1357512119.999, 1357512149.999, 1357512179.998, 
  1357512209.999, 1357512239.999, 1357512269.999, 1357512299.999, 
  1357512329.997, 1357512359.993, 1357512389.997, 1357512419.999, 
  1357512449.999, 1357512479.998, 1357512509.999, 1357512539.999, 
  1357512569.999, 1357512599.999, 1357512629.999, 1357512659.995, 
  1357512689.999, 1357512719.999, 1357512749.999, 1357512779.995, 
  1357512809.999, 1357512839.999, 1357512869.999, 1357512899.999, 
  1357512929.999, 1357512959.999, 1357512989.997, 1357513019.996, 
  1357513049.999, 1357513079.999, 1357513109.999, 1357513139.999, 
  1357513169.999, 1357513199.993, 1357513229.999, 1357513259.999, 
  1357513289.999, 1357513319.999, 1357513349.998, 1357513379.999, 
  1357513409.999, 1357513439.999, 1357513469.999, 1357513499.999, 
  1357513529.999, 1357513559.999, 1357513589.999, 1357513619.999, 
  1357513649.999, 1357513679.999, 1357513709.999, 1357513739.999, 
  1357513769.999, 1357513799.998, 1357513829.997, 1357513859.999, 
  1357513889.999, 1357513919.999, 1357513949.999, 1357513979.998, 
  1357514009.999, 1357514039.996, 1357514069.999, 1357514099.999, 
  1357514129.999, 1357514159.999, 1357514189.999, 1357514219.999, 
  1357514249.999, 1357514279.999, 1357514309.999, 1357514339.993, 
  1357514369.999, 1357514399.999, 1357514429.999, 1357514459.999, 
  1357514489.999, 1357514519.999, 1357514549.988, 1357514579.997, 
  1357514609.999, 1357514639.998, 1357514669.984, 1357514699.999, 
  1357514729.999, 1357514759.999, 1357514789.999, 1357514819.999, 
  1357514849.999, 1357514879.999, 1357514909.999, 1357514939.996, 
  1357514969.999, 1357514999.999, 1357515029.999, 1357515059.998, 
  1357515089.999, 1357515119.97, 1357515149.998, 1357515179.999, 
  1357515209.999, 1357515239.999, 1357515269.999, 1357515299.999, 
  1357515329.999, 1357515359.999, 1357515389.999, 1357515419.999, 
  1357515449.999, 1357515479.999, 1357515509.999, 1357515539.999, 
  1357515569.999, 1357515599.999, 1357515629.995, 1357515659.999, 
  1357515689.999, 1357515719.999, 1357515749.999, 1357515779.999, 
  1357515809.995, 1357515839.999, 1357515869.999, 1357515899.999, 
  1357515929.999, 1357515959.999, 1357515989.999, 1357516019.999, 
  1357516049.999, 1357516079.999, 1357516109.999, 1357516139.999, 
  1357516169.999, 1357516199.999, 1357516229.999, 1357516259.998, 
  1357516289.998, 1357516319.999, 1357516349.999, 1357516379.999, 
  1357516409.999, 1357516439.999, 1357516469.999, 1357516499.999, 
  1357516529.999, 1357516559.999, 1357516589.999, 1357516619.999, 
  1357516649.999, 1357516679.999, 1357516709.999, 1357516739.999, 
  1357516769.999, 1357516799.999, 1357516829.999, 1357516859.999, 
  1357516889.999, 1357516919.999, 1357516949.999, 1357516979.999, 
  1357517009.999, 1357517039.999, 1357517069.999, 1357517099.999, 
  1357517129.999, 1357517159.998, 1357517189.999, 1357517219.999, 
  1357517249.999, 1357517279.999, 1357517309.999, 1357517339.999, 
  1357517369.999, 1357517399.998, 1357517429.999, 1357517459.999, 
  1357517489.999, 1357517519.999, 1357517549.999, 1357517579.999, 
  1357517609.999, 1357517639.999, 1357517669.999, 1357517699.999, 
  1357517729.999, 1357517759.999, 1357517789.999, 1357517819.999, 
  1357517849.999, 1357517879.999, 1357517909.999, 1357517939.999, 
  1357517969.999, 1357517999.999, 1357518029.999, 1357518059.976, 
  1357518089.999, 1357518119.998, 1357518149.998, 1357518179.999, 
  1357518209.987, 1357518239.999, 1357518269.998, 1357518299.991, 
  1357518329.998, 1357518359.999, 1357518389.994, 1357518419.994, 
  1357518449.995, 1357518479.999, 1357518509.999, 1357518539.998, 
  1357518569.983, 1357518599.999, 1357518629.998, 1357518659.994, 
  1357518689.999, 1357518719.988, 1357518749.999, 1357518779.999, 
  1357518809.999, 1357518839.999, 1357518869.999, 1357518899.999, 
  1357518929.999, 1357518959.999, 1357518989.999, 1357519019.999, 
  1357519049.999, 1357519079.998, 1357519109.999, 1357519139.999, 
  1357519169.999, 1357519199.999, 1357519229.999, 1357519259.999, 
  1357519289.999, 1357519319.999, 1357519349.999, 1357519379.999, 
  1357519409.999, 1357519439.999, 1357519469.999, 1357519499.999, 
  1357519529.999, 1357519559.999, 1357519589.999, 1357519619.999, 
  1357519649.999, 1357519679.999, 1357519709.999, 1357519739.999, 
  1357519769.999, 1357519799.999, 1357519829.997, 1357519859.999, 
  1357519889.999, 1357519919.999, 1357519949.999, 1357519979.999, 
  1357520009.999, 1357520039.999, 1357520069.999, 1357520099.999, 
  1357520129.999, 1357520159.999, 1357520189.999, 1357520219.999, 
  1357520249.999, 1357520279.999, 1357520309.999, 1357520339.999, 
  1357520369.999, 1357520399.999), tzone = "", tclass = c("POSIXct", 
  "POSIXt"), class = c("POSIXct", "POSIXt")), count = c(20763L, 
  12030L, 22188L, 12183L, 21112L, 11628L, 21543L, 12609L, 20095L, 
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  11708L, 21476L, 12210L, 21364L, 12041L, 21907L, 11934L, 22207L, 
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  41287L, 52697L, 62618L, 78594L, 68193L, 76617L, 63747L, 90556L, 
  75830L, 104609L, 51063L, 67046L, 66977L, 82513L, 87228L, 107474L, 
  141878L, 127290L, 70953L, 98879L, 87814L, 117309L, 113463L, 150979L, 
  198271L, 170456L, 108325L, 119583L, 111803L, 117067L, 186768L, 
  226191L, 235546L, 228039L, 165570L, 159472L, 161707L, 137614L, 
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  82024L, 86640L, 77493L, 71205L, 87641L, 89232L, 99214L, 89311L, 
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  92559L, 89194L, 81721L, 83490L, 96388L, 90145L, 79861L, 90301L, 
  77676L, 262966L, 227355L, 256477L, 238905L, 241260L, 206168L, 
  229477L, 215515L, 245217L, 232026L, 225308L, 223537L, 198524L, 
  237840L, 233483L, 193081L, 216570L, 212949L, 203150L, 240861L, 
  209596L, 200673L, 180099L, 187726L, 187642L, 188402L, 176871L, 
  216090L, 203310L, 184723L, 195702L, 204137L, 276952L, 313717L, 
  323208L, 308448L, 321638L, 378236L, 352163L, 413678L, 395997L, 
  354317L, 366915L, 339465L, 346781L, 394895L, 355176L, 349618L, 
  417590L, 335474L, 405686L, 362581L, 356525L, 354142L, 383487L, 
  334305L, 327489L, 336201L, 374153L, 341485L, 321473L, 308773L, 
  15709L, 8870L, 15563L, 8944L, 15941L, 9342L, 16303L, 8951L, 14969L, 
  9385L, 14537L, 9963L, 15676L, 9011L, 16552L, 9587L, 16802L, 9693L, 
  15267L, 8946L, 14189L, 9067L, 14359L, 9776L, 167922L, 337364L, 
  350941L, 362928L, 364922L, 319641L, 348687L, 321356L, 400161L, 
  334171L, 332829L, 323842L, 397809L, 375694L, 384432L, 356825L, 
  350846L, 395942L, 359471L, 296926L, 418481L, 322144L, 335658L, 
  347212L, 334421L, 375769L, 364300L, 317370L, 373192L, 346713L, 
  356341L, 327225L, 305538L, 347815L, 276914L, 322149L, 303627L, 
  292363L, 284724L, 305082L, 373363L, 304386L, 438592L, 403579L, 
  430549L, 450536L, 432445L, 389779L, 434888L, 375010L, 456096L, 
  577393L, 451122L, 432354L, 425547L, 417729L)), .Names = c("time", 
  "count"), row.names = c(NA, -480L), class = "data.frame")
  
  &gt; dput(ev)
  structure(list(dt = structure(c(1357508700, 1357510680, 1357512540, 
  1357515360, 1357517220, 1357517700, 1357518000, 1357518000, 1357519140, 
  1357519140), class = c("POSIXct", "POSIXt"), tzone = ""), event = structure(c(7L, 
  8L, 3L, 2L, 5L, 6L, 1L, 4L, 2L, 9L), .Label = c("Event 1", 
  "Event 2", "Event 3", 
  "Event 4", "Event 5", 
  "Event 6", "Event 7", 
  "Event 8", "Event 9"
  ), class = "factor")), .Names = c("dt", "event"), row.names = c(NA, 
  -10L), class = "data.frame")
  </code></pre>
  
  <p>Library Versions:</p>
  
  <pre><code>&gt; sessionInfo()
  R version 2.15.1 (2012-06-22)
  Platform: x86_64-redhat-linux-gnu (64-bit)
  
  attached base packages:
  [1] grid      stats     graphics  grDevices utils     datasets  methods   base     
  
  other attached packages:
  [1] reshape2_1.2.2   xts_0.9-1        zoo_1.7-9        gdata_2.12.0     data.table_1.8.6 caTools_1.14    
  [7] scales_0.2.3     ggplot2_0.9.3   
  </code></pre>
  
  <p>Simplied code - this still doesnt work</p>
  
  <pre><code>library(scales)
  library(ggplot2)
  taonedf&lt;-dget("taonedf") #in this thread
  ev&lt;-dget("ev") #in this thread
  
  ggplot(data=taonedf, aes(x=time, y=count/30)) +
    geom_line() +
    geom_vline(data=ev,aes(xtintercept=as.numeric(dt)))
  </code></pre>