yAxis = (g, y) => g
.call(d3.axisLeft(y).ticks(12 * k))
.call(g => g.select(".domain").attr("display", "none"))
.call(g => g.append("text")
.style("font-size", "18px")
.attr("transform", `rotate(${-90})`)
.attr("x", -height/2)
.attr("y", -margin.left/2)
.attr("fill", "grey")
.attr("text-anchor", "middle")
.text("Percentage of Labour MPs on twitter following"))