Anyone any idea how to create a 7 day rolling average from an array of objects, to plot in a node-RED chart? The data arrives as an array of objects, comprising of a value, together with a epoch timestamp. There is just one object per day, and currently there is about 120 objects (4 months worth o…

I have assumed that for the first 6 samples what is wanted is the average of the samples so far. There are probably more compact ways of doing it but I imagine this is one of the most efficient techniques as keeps a rolling total rather than adding up seven values each time. // Expects payload to …

If you want just latest 7 days and the data is already sorted, you could (in a function node) use the array slice function followed by array reduce function. Does that help? Need more?

[image] Steve-Mcl: If you want just latest 7 days No, I want to plot the rolling 7 days average, starting from the earliest datapoint to the latest datapoint, so the chart data will absorb the anomalies. Example; the daily UK Coronavirus briefing, where accurate data is not received over a w…

the smooth node does an average over however many samples you say...

Yes, I've looked at that, but I haven't managed to handle an array of timestamped data using the node. If I strip out the data from the timestamp, and feed it as consecutive data points, I'm sure it would work, but then I've lost the timestamps, and therefore difficult to chart.

I’m not sure if I understand your needs correctly, but have you thought about supplying your data points to a function node with a reducer in it to calculate the rolling average? [image] Array.prototype.reduce() The reduce() method executes a reducer function (that you provide) on each e…

There is also a reduce mode within the join node that can be set to do whatever consolidation you want. The default example is average

The line answer[i] = {x: msg.payload[i].x, y: total/count} would have been better as answer.push( {x: msg.payload[i].x, y: total/count} )

Very clever @Colin , it's working fine on the live data, and it's also easy to switch the chart between original data and the 7 day rolling average by passing in the value of n via msg.ra with the data feed. const n = msg.ra || 7; Thank you :+1: Edit// @afelix , @dceejay I did try to use both sugge…

Because it's not the real data, it is just an example to show the format of the data, so it would be clear how the array is structured.

Dashboard Charts - 7 day rolling average

General

dceejay 23 May 2020 21:46 11

looking at your original data - why do you have duplicate x values ?

Remove duplicates from an array of objects

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Dashboard Charts - 7 day rolling average

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