react-map-gl/examples/additional-overlays/scatterplot-overlay.md
2017-06-15 18:05:49 -07:00

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# Scatter Plot Overlay
This is an example overlay that draws a scatterplot over a map using canvas. Adjust the more interesting props using the controls below.
```js
const ScatterplotOverlay = require('./scatterplot-overlay');
<MapGL {...viewport} mapStyle={mapStyle}>
<ScatterplotOverlay
locations={this.state.locations}
dotRadius={1}
globalOpacity={0.8}
compositeOperation="lighter"
dotFill="blue"
renderWhileDragging={true}
/>
</MapGL>
```
## Props
#### locations
An [ImmutableJS](https://facebook.github.io/immutable-js/) [List](https://facebook.github.io/immutable-js/docs/#/List) of points.
```js
const locations = Immutable.fromJS([
[-122.39851786165565, 37.78736425435588],
[-122.40015469418074, 37.78531678199267],
[-122.4124101516789, 37.80051001607987],
// ...
]);
```
#### lngLatAccessor
Use the `lngLatAccessor` prop to provide the location in a custom format. It's called with each location as the first argument. Here's the default `lngLatAccessor`.
```js
function lngLatAccessor(location) {
return [location.get(0), location.get(1)];
}
```
#### renderWhileDragging
If the overlay should redraw when the user is dragging the map. Default `true`.
#### dotRadius
Radius of the dots. Default `4`.
#### dotFill
Color of the dots. Default `#1FBAD6`.
#### globalOpacity
Opacity of the dots when drawing into the canvas. Default `1`.
#### compositeOperation
`globalCompositeOperation` of the canvas. This prop can be used to control blending modes.
Default `source-over`.