Multilayer Charts

You can superimpose multiple Pointmap, Linemap, Choropleth, and Geo Heatmap charts on one another to look for correlations between datasets.

To create a multilayer chart:

1. Create one of the charts that support multilayer.

2. Click the Add Layer tab.

3. Create another multilayer-compatible chart in the new layer.

4. Click the Master tab.

5. Adjust the Opacity and the Zoom level of the chart layers using the sliders on the right.

You can change the order of the layers by dragging the contents of a layer field on top of another layer field.

A single chart can have up to eight layers, depending on your server memory and processing capacity.

Example: Opacity with Multilayer Charts

Create a new Pointmap. For the Data Source, use the official database of UFO sightings.

Set the Lon measure to longitude and Lat measure to latitude. Set the Size measure to duration_seconds. Set the Color measure to shape.

Click the Add Layer tab, and create a Geo Heatmap. Set the data source to the flights_2008_7M database. Set Lon to dest_lon and Lat to dest_lat. Set the Color measure to AVG depdelay.

The resulting chart compares a Geo Heatmap of flight departure delays to a Pointmap of UFO sightings.

Click the Master tab, and reduce the opacity of the UFOs Sighted chart to enhance the visibility of the flights_2008_7M delay information.

Clearly, some flights have been delayed where UFOs have been sighted, making it impossible to make a definitive statement that there is no correlation between the two datasets. Spooky.

Example: Zoom Level with Multilayer Charts

You can configure the visibility of a layer based on zoom level.

This chart has two layers: a Pointmap based on tweets and a Choropleth based on 14 states defined by name, with the rest defined as Other. Currently, the chart is zoomed to level 5.

You determine that when you zoom to level 2, you no longer want to see the states layer, so you adjust the sliders to reflect this.