function drawTriangles(triangleCoords, selector, className) {
selector.selectAll(`.${className}`)
.data(triangleCoords)
.join(enter => enter
.append('path')
.attr("class", className)
.attr("d", function(d){
var coords = [d[0], d[1], d[2]];
return d3.line()
.x(function(d) { return d.x; })
.y(function(d) { return d.y; })
.curve(d3.curveLinear)(coords);
})
.attr("stroke", "black")
.attr("fill", function(d, i) {
return i % 2 === 0 ? "yellow" : "lightblue";
})
)
}