ttr("x", 30).attr("y", 20).text("Variable genes").style("font-size", "14px").attr("alignment-baseline","middle")
svgVST.append("text").attr("x", 30).attr("y", 40).text("Non-variable genes").style("font-size", "14px").attr("alignment-baseline","middle")


// Add X axis label:
svgVST.append("text")
    .attr("text-anchor", "middle")
    .attr("x", width/2)
    .attr("y", height - (parseInt(height/40)))
    .text("Average Expression").style("font-size",(parseInt(width/33)+"px"));

// Y axis label:
svgVST.appen