Line Chart with Circle Tooltip and arrow D3 V4

This chart is based on mbostock‘s block: Line Chart

it uses a json file storing year values and population values. The chart employs conventional margins and a number of D3 features:

• d3.json - load and parse data
• d3.tickFormat - format y axis tick text
• d3.time.scale - x-position encoding
• d3.extent - compute domains
• d3.svg.axis - display axes
• d3.svg.line - display line shape

forked from alandunning‘s block: Line Chart with Circle Tooltip D3 V4