...

		join.enter()
			.append("circle")
			.style("fill", function(x){return x.colour})
			.attr("r", 10)
			.attr("cx", function(x){return xScale(x.weight)})
			.attr("cy", function(x){return yScale(x.height)})
			.on("click", onClick)

		...

		function onClick(datum, index){
			data[index].height = 1000;
			draw(data);
		}	

		...