score:1

This is an interesting problem. The example you link to uses a single `y` scale and `yAxis` for all 4 sub-plots. In your situation, though, your data has a very different domain for each sub-plot and when you add the dynamic mouse over a shared scale just won't work. So, my solution would be to create a different `y` scale and `yAxis` for each subplot.

``````...

// variable to hold our scales
var ys = {};

var area = d3.svg.area()
.x(function(d) {
return x(d.date);
})
.y0(height)
.y1(function(d) {
return ys[d.symbol](d.price); //<-- call the y function matched to our symbol
});

var line = d3.svg.line()
.x(function(d) {
return x(d.date);
})
.y(function(d, i) {
return ys[d.symbol](d.price); //<-- call the y scale function matched to our symbol
});

...

// for each symbol create our scale
symbols.forEach(function(s) {
var maxPrice = d3.max(s.values, function(d) {
return d.price;
});
ys[s.key] = d3.scale.linear() //<-- create a scale for each "symbol" (ie Sensor 1, etc...)
.range([height, 0])
.domain([0, maxPrice]);
});

...

// build 4 y axis
var axisGs = svg.append("g"); //<-- create a collection of axisGs

axisGs
.attr("class", "y axis")
.append("text")
.attr("transform", "rotate(-90)")
.attr("y", 6)
.attr("dy", ".71em")
.style("text-anchor", "end")
.text("Value");

axisGs.each(function(d, i) { //<-- for each axisG create an axis with it's scale
var self = d3.select(this);
self.call(
d3.svg.axis()
.scale(ys[d.key])
.orient("left")
.ticks(4)
);
});

...

// adjust mouseover to use appropriate scale
focus.attr("transform", function(d) {
index = bisectDate(d.values, date, 0, d.values.length - 1);
console.log(index, d.values[index].symbol, d.values[index].date, d.values[index].price);
return "translate(" + x(d.values[index].date) + "," + ys[d.key](d.values[index].price) + ")"; //<-- finally in our mouse move use the appropriate scale
});
``````

Fully working code here.

score:1

As far as best practices are concerned when you are dealing with n number of datasets you have to go for n number of y scales and their corresponding y axis. It is good for seperation of concern and keeps the visulization intact. here you can see the example.