function addReferenceLines(sel, svg, referenceValues, c) {
    var gRef = void 0;
    var data = void 0;
    var referenceLine = d3.line().x(ƒ("year", c.x)).y(ƒ("value", c.y)).curve(d3.curveMonotoneX);

    referenceValues.forEach(function (ref, i) {
      data = ref.value.map(function (ele, index) {
        return {
          year: index,
          value: ele[Object.keys(ele)[0]]
        };
      });
      data.text = ref.text;
      data.anchor = parsePosition(ref.textPosition);
      data.offset = getOffset(data.anchor);

      gRef = svg.append("g").attr("class", "reference question-referenceValues referenceLine controls line-" + data.text.trim());

      gRef.append("path").attr("d", referenceLine(data)).attr("class", "line referencePath").attr("id", "curvedPath-" + i);

      gRef.append("text").attr("class", "question-referenceText update-font").attr("dy", "-5").append("textPath").attr("class", "referenceTextPath").attr("text-anchor", data.anchor).attr("startOffset", data.offset).attr("xlink:href", "#curvedPath-" + i).text(data.text);
    });
  }
/* 
   * params:
   * sel: DOM selection for the text label of the reference value. A <span> is added with the text
   * svg: SVG for the lines connecting the graph with the label
   * referenceValues: question.referenceValues
   * c: object constant with graphical DOM selections as properties
   */
DOM selection for the text label of the reference value. A  is added with the text
svg: SVG for the lines connecting the graph with the label
referenceValues: question.referenceValues
c: object constant with graphical DOM selections as properties
DOM selection for the text label of the reference value . A is added with the text svg : SVG for the lines connecting the graph with the label referenceValues : question . referenceValues c : object constant with graphical DOM selections as properties
function addReferenceLines(sel, svg, referenceValues, c) {
    var gRef = void 0;
    var data = void 0;
    var referenceLine = d3.line().x(ƒ("year", c.x)).y(ƒ("value", c.y)).curve(d3.curveMonotoneX);
    referenceValues.forEach(function (ref, i) {
      data = ref.value.map(function (ele, index) {
        return {
          year: index,
          value: ele[Object.keys(ele)[0]]
        };
      });
      data.text = ref.text;
      data.anchor = parsePosition(ref.textPosition);
      data.offset = getOffset(data.anchor);
      gRef = svg.append("g").attr("class", "reference question-referenceValues referenceLine controls line-" + data.text.trim());
      gRef.append("path").attr("d", referenceLine(data)).attr("class", "line referencePath").attr("id", "curvedPath-" + i);
      gRef.append("text").attr("class", "question-referenceText update-font").attr("dy", "-5").append("textPath").attr("class", "referenceTextPath").attr("text-anchor", data.anchor).attr("startOffset", data.offset).attr("xlink:href", "#curvedPath-" + i).text(data.text);
    });
  }
function addReferenceLines ( sel , svg , referenceValues , c ) { var gRef = void 0 ; var data = void 0 ; var referenceLine = d3 . line ( ) . x ( ƒ( " year", . x ) ) . y ( ƒ (" v alue",  c y ) ) . c u rve(d 3 .c u rveMonotoneX); referenceValues . forEach ( function ( ref , i ) { data = ref . value . map ( function ( ele , index ) { return { year : index , value : ele [ Object . keys ( ele ) [ 0 ] ] } ; } ) ; data . text = ref . text ; data . anchor = parsePosition ( ref . textPosition ) ; data . offset = getOffset ( data . anchor ) ; gRef = svg . append ( "g" ) . attr ( "class" , "reference question-referenceValues referenceLine controls line-" + data . text . trim ( ) ) ; gRef . append ( "path" ) . attr ( "d" , referenceLine ( data ) ) . attr ( "class" , "line referencePath" ) . attr ( "id" , "curvedPath-" + i ) ; gRef . append ( "text" ) . attr ( "class" , "question-referenceText update-font" ) . attr ( "dy" , "-5" ) . append ( "textPath" ) . attr ( "class" , "referenceTextPath" ) . attr ( "text-anchor" , data . anchor ) . attr ( "startOffset" , data . offset ) . attr ( "xlink:href" , "#curvedPath-" + i ) . text ( data . text ) ; } ) ; }
params:
 sel: DOM selection for the text label of the reference value.
params : sel : DOM selection for the text label of the reference value .