D3: SVG Line Graph Area

Adapted to D3.js v4 from v3

• .attrs({}) v4 method contains multiple attribute tuples. Replacing v3’s .attr({}).
• d3.area() v4 method replaces v3’s d3.svg.area().

Forked v4 script above. Original v3 script below.

D3.js 3.5.17 seems to have a similar existence to Python 2.7.14. Maintained to avoid alienating v3 users.