Unable to get the zoom object

Nobody has claimed this yet.

Hello everybody!

I'm currently using EventDrops in an Angular 4 application. I need to set the zoom programmatically, so I read the documentation and the example:

```
var eventDropsChart = d3.chart.eventDrops();
var element = d3.select('#chart_placeholder').datum(...);
eventDropsChart.call(eventDropsChart);
var zoom = element[0][0].zoom;
```

I have something similar in my code:

```
var chart = d3.chart.eventDrops()
.date(d => d.date)
.start(minDate)
.end(maxDate)
.mouseover(this.showTooltip)
.mouseout(this.hideTooltip)
.click(this.onEventClick)
.zoomend(this.onZoomEnd)
.eventLineColor((d, i) => colors[i]);

this.timeline = d3.select('#visual')
.datum(data)
.call(chart);

console.log("ZOOM");
console.log(this.timeline[0]); // Ouptut: undefined
```

but then I got undefined, so I'm unable to get the zoom.

I also tried to change the code to:

```
this.timeline = d3.select('#visual')
.datum(data);

chart.call(chart);

console.log("ZOOM");
console.log(this.timeline[0]);
```

But then I got another error:

> Cannot read property 'each' of undefined
> at Function.e (eventDrops.js:1)

Is it a bug or am I doing something wrong?

Thanks!

The report centers on eventDrops.js and the documented chart.call and selection snippets; start by comparing those invocation paths and how the zoom object is attached to the rendered selection. Reproduce the Angular 4 case, then verify whether the documented way to access zoom works or needs correction.

Written by the indexing model from the issue text.