Hi, I’m very glad to have the detailed real-time and recent data of PurpleAir. I’m confused, though, by the differences I’ve noticed between the value shown in the map dot and the latest value in the graph over time. I expect them to be the same, but often they are not, by a large margin. Example: …

Hi @whiwal , we have just posted a new topic regarding this issue. You can find it here: Difference in Graph and Marker Data .

Thanks very much, Ethan. That’s interesting. In signal processing (where I’m rusty), I believe “infinite impulse response (IIR) filter” is a better name for the method that is described on your linked page as a “weighted moving average.” The code shown matches an IIR, but the description is inaccur…

@Ethan the post you linked does not explain the discrepancy with the US EPA conversion. If you look at the first screenshot in @whiwal ’s post, the Map Marker shows the “Now” AQI as 282, whereas in the graph you can clearly see the AQI has never exceeded 250 (and is generally below 200). I’m noticin…

@pbhuss , since two different averages are being used, you may not be able to compare the reading on the map marker to the readings in the graph. If a graph was made of the weighted moving average values, the spikes in the graph might jump up much higher than 250. As you can see in @whiwal ’s first sc…

@Ethan , please take a look at the deeper discussion of this same problem in another thread: [image] Values shown on map don't match the sensor time series when EPA conversion is applied Bug Reports Found the bug, in the class definition for the US EPA conversion (in the Mo…

Discrepancy between current value on dot and in graph

Real-Time Map

whiwal October 20, 2022, 9:40pm 6

@Ethan, please take a look at the deeper discussion of this same problem in another thread:

Topic		Replies	Views
Real-time data on Map Markers and graph do not match for US EPA conversion Bug Reports	0	423	October 15, 2022
Difference in Graph and Map Marker Data Real-Time Map	0	735	October 10, 2022
Values shown on map don't match the sensor time series when EPA conversion is applied Bug Reports	5	782	October 30, 2023
How to Use the Map Graph Real-Time Map	16	197501	December 1, 2023
Negative AQI Real-Time Map	6	671	October 3, 2023

Discrepancy between current value on dot and in graph

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