           .attr("opacity", 0)
           .on("mouseover", (td) ->
                  d3.select(this).attr("opacity", 1) unless markerClick[td]
-                 tip.call(this,td))
+                 martip.call(this,td))
           .on "mouseout", (td) ->
                  d3.select(this).attr("opacity", markerClick[td])
-                 d3.selectAll("#d3tip").remove()
+                 d3.selectAll("#martip").remove()
           .on "click", (td) ->
                  pos = data.lod[chr].pos[data.markerindex[chr][td]]
                  title = "#{td} (chr #{chr}, #{onedig(pos)} cM)"


  # Using https://github.com/Caged/d3-tip
  #   [slightly modified in https://github.com/kbroman/d3-tip]
  tip = d3.svg.tip()
          .orient("right")
          .padding(3)
          .text((z) -> z)
          .attr("class", "d3-tip")
          .attr("id", "d3tip")

  markerClick = []


            "red")
         .attr("stroke", "black")
         .attr("stroke-width", "2")
         .on("mouseover", efftip)
         .on("mouseout", -> d3.selectAll("#efftip").remove())


  # background rectangles for each chromosome, alternate color
