     d3.select("div#chart3")
       .datum(data2pass)
       .call(mychart)
-
-

    markers = ["DXM64", "DXM66"]
    mychart = crosstab()

    data2pass = 
            x: data.geno[markers[0]]
            y: data.geno[markers[1]]
            xcat: data.genocat[data.chrtype[markers[0]]]

    markers = ["D1M430", "DXM64"]
    mychart = crosstab()

    data2pass =
            x: data.geno[markers[0]]
            y: data.geno[markers[1]]
            xcat: data.genocat[data.chrtype[markers[0]]]
