/** Adds a simple marker with the average visit duration */
function drawDurationChart(durationMeanSec) {
	var dMarkerRadius = 32;
	var dMarkerStrokeWidth = 3; // Match with CSS
	var chartWidth = 150, chartHeight = 150,
		xPos = 40, yPosStart = chartHeight, yPosEnd = 0, // Start / End are for the animation
		lineHeight = 28, bottomOffset = lineHeight; // bottomOffset = lineHeight * 2;
	var durationSvg = d3.select('.durationChart').append('svg')
		.attr('width',	chartWidth)
		.attr('height', chartHeight);
	// Add a group for the marker elements in the animation start state
	var markerG = durationSvg.append('g')
		.attr('class', 'marker duration')
		.attr('transform', 'translate(' + xPos + ', ' + yPosStart + ')')
		.attr('opacity', 0);
	// Animate the group to appear with opacity and translate animation
	markerG
		.transition()
		.duration(1000)
		.attr('transform', 'translate(' + xPos + ', ' + yPosEnd + ')')
		.attr('opacity', 1);
	// The marker elements are now relative positioned to the group
	markerG.append('path') // The marker line
		.attr('d', 'M' + dMarkerRadius + ',' + (chartHeight - bottomOffset - yPosStart) + 'L' + dMarkerRadius + ',' + (chartHeight-yPosStart))
		.transition()
			.duration(1000)
			.attr('d', 'M' + dMarkerRadius + ',' + (chartHeight - bottomOffset - yPosEnd) + 'L' + dMarkerRadius + ',' + (dMarkerRadius*2));
	markerG.append('path')
		.attr('class', 'marker-bg hexagon')
		.attr('d', hexagon(dMarkerRadius, dMarkerRadius, dMarkerRadius - dMarkerStrokeWidth / 2));
	markerG.append('image')
		.attr('width', '' + dMarkerRadius * 2 * 0.6)
		.attr('height', '' + dMarkerRadius * 2 * 0.6)
		.attr('x', '' + dMarkerRadius * 2 * 0.2)
		.attr('y', '' + dMarkerRadius * 2 * 0.2)
		.attr('href', 'clock-o.svg');
// 	markerG.append('text')
// 		.attr('x', dMarkerRadius)
// 		.attr('y', chartHeight - bottomOffset + lineHeight)
// 		.text('Duration');
	markerG.append('text')
		.attr('x', dMarkerRadius)
		.attr('y', chartHeight - bottomOffset + lineHeight)
// 		.attr('y', chartHeight - bottomOffset + lineHeight * 2)
		.text('∅ ' + d3.format('.1f')(durationMeanSec) + ' s');
}