     plotPXG = (marker) ->
       d3.selectAll(".plotPXG").remove()
 
+      pxgXaxis = svg.append("g").attr("class", "probe_data").attr("class", "plotPXG").attr("id", "pxg_xaxis")
       pxgYscale = d3.scale.linear()
                      .domain([d3.min(probe_data.pheno),
                               d3.max(probe_data.pheno)])

  lightGray = d3.rgb(230, 230, 230)
  darkGray = d3.rgb(200, 200, 200)
  darkblue = "darkslateblue"
  darkgreen = "darkgreen"
  pink = "hotpink"
  altpink = "#E9CFEC"
  purple = "#8C4374"

      for i of means
        means[i] /= n[i]

      pxgXaxis.selectAll("empty")
              .data(means)
              .enter()
