Yes, I've started writing JS now :|

gistfile1.txt

$( function () {
	globalData = [];
	var placeholder = $("#placeholder");
	$.plot(placeholder, [[]], options);
	var num_points = 300;

	function onDataReceived(data_point) {
		globalData.push(data_point.data + ( Math.random() * 10));

		var res = [];
		for (var i = 0; i < globalData.length; ++i) {
			res.push([i, globalData[i]])
		}
		$.plot(placeholder, [ res ], options);
	}

	function plotData() {
		if ( globalData.length > num_points) {
			globalData = globalData.slice(1);
		}

		var jqxhr = $.ajax({
			url: "/pig.json",
			method: 'GET',
			dataType: 'json',
			success: onDataReceived
		});

	}

	var updateInterval = 1000;
	$("#updateInterval").val(updateInterval).change( function () {
		var v = $(this).val();
		if (v && !isNaN(+v)) {
			updateInterval = +v;
			if (updateInterval < 1)
				updateInterval = 1;
			if (updateInterval > 2000)
				updateInterval = 2000;
			$(this).val("" + updateInterval);
		}
	});
	// setup plot
	var options = {
		series: {
			shadowSize: 0
		},
		yaxis: {
			min: 0,
			max: 50
		},
		xaxis: {
			show: false
		}

	};

	function update() {
		plotData();
		setTimeout(update, updateInterval);
	}

	update();
});

What are you trying to plot?