visF.append("rect")
 .attr("class", "background")
 .attr("width", width)
 .attr("height", height)
 .call(d3.behavior.zoom().on("zoom", redrawVisF));
function redrawVisF () {
  visF.attr("transform","translate(" + d3.event.translate + ")" + " scale(" + d3.event.scale + ")");
}