The PurpleAir Map supports a powerful graph feature that allows you to easily view data from sensors. This is useful when looking to understand the recent history of a device and its air quality readings. This article outlines what you’re able to do with the graph.
This article will use terms and concepts specific to the PurpleAir map. If you haven’t already, we recommend reading our PurpleAir Map Guide to familiarize yourself.
Opening the Map Graph
The PurpleAir Map displays recent historical data in an interactive line graph. To open the graph, follow the steps below.
- Open the PurpleAir map.
- Click on a sensor’s map marker, this will open the graph.
- What is shown on the graph reflects your current map settings, including your selected data layer, conversion, and averaging period.
| Map Setting | Purpose |
|---|---|
| Data Layer | This is the type of data you’re looking at. If you have the US EPA AQI selected, the graph will show AQI values. But if you have temperature selected, it will show temperature data. These are only two examples; many other data layers exist. |
| Apply Conversion | If you have any conversion applied, the graph data will reflect that conversion. Conversions help accommodate different types of pollution in different areas and situations. |
| Averaging Period | The averaging period determines what average of data you’re looking at. If you have real-time selected, you’re looking at a two-minute average, which is a single value that represent the past two minutes of data. If you have 10-minute selected, you’re looking at 10 minute averages. Each point on the graph is one of these averages. |
To close the graph, click or tap the “x” in the top-right corner of the configuration menu.
Hovering over or tapping a point on the graph will display its value along with the exact date and time of the reading.
You’ll also notice that when you click on an outdoor sensor, two lines appear in the graph. These are the two channels in your device.
Zooming in on the Graph
Zooming in allows you to focus on a specific time range and adjust the y-axis to new minimum and maximum values.
Zooming in on a Computer
To zoom in on a computer, click and drag your mouse over a section of the graph. A colored box will appear to indicate the section you’re zooming in to. Release the mouse to zoom in.
While zoomed in, you can pan left or right by clicking and dragging the graph while holding down the Shift key.
Zooming in on a Mobile Device
When using a mobile device, spread with two fingers on the graph to zoom in, just as you would on most websites.
Resetting the Zoom
To return to the default view, click the “Reset zoom” button below the graph. This button only appears after zooming in. On a mobile device, you can also pinch with two fingers to zoom out.
Additional Information
Viewing Multiple Sensors
The graph can display and compare data from multiple sensors simultaneously. With the graph open, click on another sensor to add its readings to the same view. You can add as many sensors as you like for side-by-side comparison.
To highlight or isolate a specific channel of data, hover your mouse over its name at the bottom of the graph.
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Clicking or tapping the channel name toggles its visibility in the graph. This is especially helpful when one sensor channel is experiencing an issue and reporting erroneous values. You can simply click on its name at the bottom to hide it from view.
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The dashed gray line represents the average of all displayed data.
Viewing Older Data
The amount of data shown in the graph depends on the selected averaging period. Larger averages allow you to view longer periods of historical data.
| Selected Average | Visible Data |
|---|---|
| Real-time | 2 days |
| 10-minute | 3 days |
| 30-minute | 7 days |
| 1-hour | 14 days |
| 6-hour | 90 days |
| 1-day | 1 year |
| 1-week | 5 years |
| 1-month | 20 years |
| 1-year | 100 years |
To access older data with a smaller averaging period, you can query it from the PurpleAir API.
Fullscreen Mode and Download Options
Click or tap the hamburger menu ☰ on the graph window for additional options.
- Select “View in full screen” to expand the graph to fill your screen.
- When in full screen, the option changes to “Exit full screen.”
You can also download the graph as an image (PNG, JPG, PDF, or SVG) or export the underlying data as a CSV or XLS file.
For more details, see How to Download Map Graph Data.
You can also use the PurpleAir API to download and analyze data from multiple sensors, across any averaging period, and for any time range.
