title: R parallel coordinate plot with fixed scale on X-axis, no matter how large the plot becomes
body: <p>I am trying to <strong>build a parallel coordinate diagram in R</strong> for showing the difference in ranking in different age groups. And I want to have a fixed scale on the Y axis for showing the values. </p>
  
  <p>Here is a PC plot : 
  <img src="https://i.stack.imgur.com/ecVvI.jpg" alt="enter image description here"></p>
  
  <p><strong>The goal is to see the slopes of the lines really well</strong>. So if I have value 1 that is bound with the value 1000, I want to see the line going aaall the way down steeply. </p>
  
  <p>In R so far, if I have values that are too big, my plot is all squished so everything fits and it's hard to visualize anything. </p>
  
  <p>My code for drawing the parallel coordinate plot is the following so far: </p>
  
  <pre><code>pc_18_34 &lt;- read.table("parCoordData_18_24_25_34.csv", header=FALSE, sep="\t")
  #name columns of data frame
  colnames(pc_18_34) = c("18-25","25-34")
  
  #build the parallel coordinate plot
  # doc : http://docs.ggplot2.org/current/geom_path.html
  group &lt;- rep(c("Top 10", "Top 10-29", "Top 30-49"), each = 18)
  df &lt;- data.frame(id = seq_along(group), group, pc_18_34[,1], pc_18_34[,2])
  colnames(df)[3] = "18-25"
  colnames(df)[4] = "25-34"
  library(reshape2) # for melt
  
  dfm &lt;- melt(df, id.var = c("id", "group"))
  dfm[order(dfm$group,dfm$ArtistRank,decreasing=TRUE),]
  colnames(dfm)[3] = "AgeGroup"
  colnames(dfm)[4] = "ArtistRank"
  
  ggplot(dfm, aes(x=AgeGroup, y=ArtistRank, group = id, colour = group), main="Tops across age groups")+  geom_path(alpha = 0.5, size=1) + geom_path(aes(color=group))
  </code></pre>
  
  <p>I have looked into how to get the scales to change in ggplot, using libraries like scales but when I had a layer of scale, the diagram doesn't even show up anymore. </p>
  
  <p><strong>Any thoughts on how to make to use a fixed scale</strong> (say difference of 1 in rank shown as 5px in the plot), <strong>even if it means that the plot is very tall</strong> ?</p>
  
  <p>Thaanks !! :)</p>