function drawVerticalMarker(){
            if (!verticalMarkerContainer) {
                verticalMarkerContainer = svg.select('.metadata-group')
                  .append('g')
                    .attr('class', 'hover-marker vertical-marker-container')
                    .attr('transform', 'translate(9999, 0)');

                verticalMarkerLine = verticalMarkerContainer.selectAll('path')
                    .data([{
                        x1: 0,
                        y1: 0,
                        x2: 0,
                        y2: 0
                    }])
                    .enter()
                      .append('line')
                        .classed('vertical-marker', true)
                        .attr('x1', 0)
                        .attr('y1', chartHeight)
                        .attr('x2', 0)
                        .attr('y2', 0);
            }
        }
Creates the vertical marker
@return void