** Copied from https://bl.ocks.org/mbostock/3887118 Then updated to D3 V4 **
This scatterplot is constructed from a TSV file storing the dimensions of sepals and petals of various iris flowers. The chart employs conventional margins and a number of D3 features:
- d3.tsv - load and parse data
- d3.scale.linear - x- and y-position encoding
- d3.scale.ordinal - color encoding
- d3.extent - compute domains
- d3.svg.axis - display axes