title: Plots for more than one series with "sparkTable" package
body: <p>If I understand it correctly, the <code>sparkTable</code> package allows for multiple kinds of plots, but only on one series. So, for example, if my dataset <code>df</code> looks like this:</p>
  
  <blockquote>
  <pre><code>variable  value   time
  Level_1   34  1947
  Level_1   38  1948
  Level_1   17  1949
  Level_1   61  1950
  Level_1   19  1951
  Level_1   80  1952
  Level_1   57  1953
  Level_1   66  1954
  </code></pre>
  </blockquote>
  
  <p>i.e. the variable "value" changes over "time" across the levels of "variable", then I can draw, for instance, sparklines and bargraphs of "value" for different levels of "variable" with the following code:</p>
  
  <pre><code>library(sparkTable)
  content&lt;-list()
  content[['LinePlot']]&lt;-newSparkLine()
  content[['BarPlot']]&lt;-newSparkBar()
  
  varType&lt;-rep("value",2)
  df&lt;-df[,c("variable","value","time")]
  df$time&lt;-as.numeric(as.character(df$time))
  dat&lt;-reshapeExt(df,idvar="variable",varying=list(2))
  sparkTab&lt;-newSparkTable(dat,content,varType)
  plotSparkTable ( sparkTab , outputType = "html", filename = "t1")
  </code></pre>
  
  <p>But is there any way to graph more than one series in the same output? For example, let's say I want to have one sparkline for "value", and another for cumulative of the "value" series over time (calculated by <code>Cumulative_Value = ave(df$value, df$variable, FUN=cumsum)</code>)</p>