# How can I specify the message path to use reduce on multiple arrays to get an average value?

**URL:** <https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836>\
**Category:** General\
**Created:** [5 April 2022 15:18 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836 "2022-04-05T15:18:44Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![mikefila](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/mikefila/32/95223_2.png) [@mikefila](https://discourse.nodered.org/u/mikefila)\
**Post date:** [5 April 2022 15:18 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836/1 "2022-04-05T15:18:45Z")

</div>

I would like to isolate `state` and then output an average of all the values.

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/5/a/5a6d4608186a2c8983dae673b2580bd1e9cc0d2c.png)

---

<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [5 April 2022 16:08 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836/2 "2022-04-05T16:08:22Z")

</div>

First look here to see how to extract the value of "state":  
[https://nodered.org/docs/user-guide/messages](https://nodered.org/docs/user-guide/messages)

Then install this node, which will average the data (among other possibilities).

> **[node-red-node-smooth](https://flows.nodered.org/node/node-red-node-smooth)**
>
> A Node-RED node that provides several simple smoothing algorithms for incoming data values.

---

<div class="post-metadata">

**Author:** ![E1cid](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/e1cid/32/77971_2.png) [@E1cid](https://discourse.nodered.org/u/E1cid)\
**Post date:** [5 April 2022 16:12 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836/3 "2022-04-05T16:12:36Z")

</div>

Or using a change node and JSONata

```auto
$sum($$.payload.State)/$count($$.payload)

```

```auto
[{"id":"225951dd.1e6fce","type":"change","z":"bf9e1e33.030598","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"$sum($$.payload.State)/$count($$.payload)","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":380,"y":2660,"wires":[["298f044.73ac97c"]]},{"id":"baf409c9.fa41f","type":"inject","z":"bf9e1e33.030598","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"sensor/hall","payload":"[{\"State\":26,\"Elevation\":79,\"Azimuth\":200,\"SNR\":24},{\"State\":16,\"Elevation\":56,\"Azimuth\":297,\"SNR\":14},{\"State\":27,\"Elevation\":27,\"Azimuth\":263,\"SNR\":33},{\"State\":31,\"Elevation\":31,\"Azimuth\":20,\"SNR\":null}]","payloadType":"json","x":210,"y":2660,"wires":[["225951dd.1e6fce"]]},{"id":"298f044.73ac97c","type":"debug","z":"bf9e1e33.030598","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":630,"y":2620,"wires":[]}]

```

[edit]  
Or using Javascript reduce()

```auto
msg.payload = msg.payload.reduce((a,o) => a+o.State, 0)/msg.payload.length
return msg;

```

---

<div class="post-metadata">

**Author:** ![mikefila](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/mikefila/32/95223_2.png) [@mikefila](https://discourse.nodered.org/u/mikefila)\
**Post date:** [5 April 2022 18:30 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836/4 "2022-04-05T18:30:17Z")

</div>

Thanks but it still doesn't give me an average. I get `NaN` from the function node and the change node removes the array and `msg.payload`

![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/9/b/9b96d350f59c886cb8cf7d0416a8183fea4c5c4a.png)

Here is a sample of the message object

```auto
{"_msgid":"f616c329e8523667","payload":[{"entity_id":"sensor.flue_temp_2","state":"142.7","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:20:02.246000+00:00","last_updated":"2022-04-05T15:20:02.246000+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.9","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:20:03.672423+00:00","last_updated":"2022-04-05T15:20:03.672423+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.7","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:20:43.669638+00:00","last_updated":"2022-04-05T15:20:43.669638+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.5","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:21:03.676032+00:00","last_updated":"2022-04-05T15:21:03.676032+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.3","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:21:43.666748+00:00","last_updated":"2022-04-05T15:21:43.666748+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.5","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:22:43.666785+00:00","last_updated":"2022-04-05T15:22:43.666785+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.2","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:23:43.664397+00:00","last_updated":"2022-04-05T15:23:43.664397+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.0","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:24:03.666374+00:00","last_updated":"2022-04-05T15:24:03.666374+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.2","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:25:03.660469+00:00","last_updated":"2022-04-05T15:25:03.660469+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.0","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:26:03.673606+00:00","last_updated":"2022-04-05T15:26:03.673606+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.8","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:26:23.661876+00:00","last_updated":"2022-04-05T15:26:23.661876+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.0","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:27:03.658066+00:00","last_updated":"2022-04-05T15:27:03.658066+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.8","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:27:23.658466+00:00","last_updated":"2022-04-05T15:27:23.658466+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.6","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:28:03.654743+00:00","last_updated":"2022-04-05T15:28:03.654743+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.8","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:28:23.655354+00:00","last_updated":"2022-04-05T15:28:23.655354+00:00"},{"entity_id":"sensor.flue_temp_2","state":"142.0","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:29:03.655387+00:00","last_updated":"2022-04-05T15:29:03.655387+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.8","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:29:43.655714+00:00","last_updated":"2022-04-05T15:29:43.655714+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.6","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:30:03.650736+00:00","last_updated":"2022-04-05T15:30:03.650736+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.4","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:30:23.657342+00:00","last_updated":"2022-04-05T15:30:23.657342+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.3","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:31:23.650141+00:00","last_updated":"2022-04-05T15:31:23.650141+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.4","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:31:43.650150+00:00","last_updated":"2022-04-05T15:31:43.650150+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.3","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:32:43.641666+00:00","last_updated":"2022-04-05T15:32:43.641666+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.1","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:33:03.641155+00:00","last_updated":"2022-04-05T15:33:03.641155+00:00"},{"entity_id":"sensor.flue_temp_2","state":"141.3","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:34:23.638284+00:00","last_updated":"2022-04-05T15:34:23.638284+00:00"},{"entity_id":"sensor.flue_temp_2","state":"140.9","attributes":{"state_class":"measurement","unit_of_measurement":"°F","device_class":"temperature","icon":"mdi:thermometer","friendly_name":"Flue Temp"},"last_changed":"2022-04-05T15:34:43.644877+00:00","last_updated":"2022-04-05T15:34:43.644877+00:00"}],"topic":"","startdate":"2022-04-05T15:20:02.246Z","enddate":"2022-04-05T15:35:02.250Z","entity_id":"sensor.flue_temp_2"}

```

---

<div class="post-metadata">

**Author:** ![E1cid](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/e1cid/32/77971_2.png) [@E1cid](https://discourse.nodered.org/u/E1cid)\
**Post date:** [5 April 2022 18:50 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836/5 "2022-04-05T18:50:40Z")

</div>

try

```auto
[{"id":"94dcf8db.04a2a","type":"inject","z":"bf9e1e33.030598","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"[{\"id\":1,\"month\":\"january\",\"temperature\":65},{\"id\":2,\"month\":\"january\",\"temperature\":28},{\"id\":3,\"month\":\"january\",\"temperature\":38},{\"id\":4,\"month\":\"february\",\"temperature\":59},{\"id\":6,\"month\":\"february\",\"temperature\":38},{\"id\":7,\"month\":\"march\",\"temperature\":80},{\"id\":8,\"month\":\"march\",\"temperature\":40},{\"id\":9,\"month\":\"march\",\"temperature\":20},{\"id\":11,\"month\":\"april\",\"temperature\":19},{\"id\":12,\"month\":\"april\",\"temperature\":49},{\"id\":13,\"month\":\"may\",\"temperature\":56},{\"id\":14,\"month\":\"may\",\"temperature\":86},{\"id\":16,\"month\":\"june\",\"temperature\":55},{\"id\":18,\"month\":\"june\",\"temperature\":40},{\"id\":19,\"month\":\"july\",\"temperature\":40},{\"id\":20,\"month\":\"july\",\"temperature\":90},{\"id\":21,\"month\":\"july\",\"temperature\":20}]","payloadType":"json","x":90,"y":2480,"wires":[["6e21e320.21444c"]]},{"id":"6e21e320.21444c","type":"function","z":"bf9e1e33.030598","name":"","func":"msg = {\"_msgid\":\"f616c329e8523667\",\"payload\":[{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.7\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:20:02.246000+00:00\",\"last_updated\":\"2022-04-05T15:20:02.246000+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.9\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:20:03.672423+00:00\",\"last_updated\":\"2022-04-05T15:20:03.672423+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.7\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:20:43.669638+00:00\",\"last_updated\":\"2022-04-05T15:20:43.669638+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.5\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:21:03.676032+00:00\",\"last_updated\":\"2022-04-05T15:21:03.676032+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.3\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:21:43.666748+00:00\",\"last_updated\":\"2022-04-05T15:21:43.666748+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.5\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:22:43.666785+00:00\",\"last_updated\":\"2022-04-05T15:22:43.666785+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.2\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:23:43.664397+00:00\",\"last_updated\":\"2022-04-05T15:23:43.664397+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.0\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:24:03.666374+00:00\",\"last_updated\":\"2022-04-05T15:24:03.666374+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.2\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:25:03.660469+00:00\",\"last_updated\":\"2022-04-05T15:25:03.660469+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.0\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:26:03.673606+00:00\",\"last_updated\":\"2022-04-05T15:26:03.673606+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.8\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:26:23.661876+00:00\",\"last_updated\":\"2022-04-05T15:26:23.661876+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.0\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:27:03.658066+00:00\",\"last_updated\":\"2022-04-05T15:27:03.658066+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.8\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:27:23.658466+00:00\",\"last_updated\":\"2022-04-05T15:27:23.658466+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.6\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:28:03.654743+00:00\",\"last_updated\":\"2022-04-05T15:28:03.654743+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.8\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:28:23.655354+00:00\",\"last_updated\":\"2022-04-05T15:28:23.655354+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"142.0\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:29:03.655387+00:00\",\"last_updated\":\"2022-04-05T15:29:03.655387+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.8\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:29:43.655714+00:00\",\"last_updated\":\"2022-04-05T15:29:43.655714+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.6\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:30:03.650736+00:00\",\"last_updated\":\"2022-04-05T15:30:03.650736+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.4\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:30:23.657342+00:00\",\"last_updated\":\"2022-04-05T15:30:23.657342+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.3\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:31:23.650141+00:00\",\"last_updated\":\"2022-04-05T15:31:23.650141+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.4\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:31:43.650150+00:00\",\"last_updated\":\"2022-04-05T15:31:43.650150+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.3\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:32:43.641666+00:00\",\"last_updated\":\"2022-04-05T15:32:43.641666+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.1\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:33:03.641155+00:00\",\"last_updated\":\"2022-04-05T15:33:03.641155+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"141.3\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:34:23.638284+00:00\",\"last_updated\":\"2022-04-05T15:34:23.638284+00:00\"},{\"entity_id\":\"sensor.flue_temp_2\",\"state\":\"140.9\",\"attributes\":{\"state_class\":\"measurement\",\"unit_of_measurement\":\"°F\",\"device_class\":\"temperature\",\"icon\":\"mdi:thermometer\",\"friendly_name\":\"Flue Temp\"},\"last_changed\":\"2022-04-05T15:34:43.644877+00:00\",\"last_updated\":\"2022-04-05T15:34:43.644877+00:00\"}],\"topic\":\"\",\"startdate\":\"2022-04-05T15:20:02.246Z\",\"enddate\":\"2022-04-05T15:35:02.250Z\",\"entity_id\":\"sensor.flue_temp_2\"}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":250,"y":2480,"wires":[["e96f33ae.be541"]]},{"id":"e96f33ae.be541","type":"function","z":"bf9e1e33.030598","name":"","func":"msg.payload = msg.payload.reduce((a,o) => a+Number(o.state), 0)/msg.payload.length\nreturn msg;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":480,"y":2540,"wires":[["298f044.73ac97c"]]},{"id":"298f044.73ac97c","type":"debug","z":"bf9e1e33.030598","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":710,"y":2600,"wires":[]}]

```

```auto
msg.payload = msg.payload.reduce((a,o) => a+Number(o.state), 0)/msg.payload.length
return msg;

```

as the state is a string it needs converting

JSONata

```auto
$sum($$.payload.$number(state))/$count($$.payload)

```

---

<div class="post-metadata">

**Author:** ![mikefila](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/mikefila/32/95223_2.png) [@mikefila](https://discourse.nodered.org/u/mikefila)\
**Post date:** [5 April 2022 19:09 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836/6 "2022-04-05T19:09:27Z")

</div>

That's perfect thank you. With reduce, how do you get to `((a,o) => a+Number(o.state), 0)`? I understand `number` but `o.state`?

---

<div class="post-metadata">

**Author:** ![E1cid](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/e1cid/32/77971_2.png) [@E1cid](https://discourse.nodered.org/u/E1cid)\
**Post date:** [5 April 2022 19:57 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836/7 "2022-04-05T19:57:08Z")

</div>

This may explain better than me. [Array.prototype.reduce() - JavaScript | MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce)

((a,o) - a is the output(accumulator) and o is the value(in this case an object) of each array value. You can give any property name you wish there and reference later in the following function.

=\> is the arrow function expression. [Arrow function expressions - JavaScript | MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions)

a+Number(o.state) - o.state is, o the object, and state the property.

0 - is the initial state of a

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [19 April 2022 19:57 UTC](https://discourse.nodered.org/t/how-can-i-specify-the-message-path-to-use-reduce-on-multiple-arrays-to-get-an-average-value/60836/8 "2022-04-19T19:57:43Z")

</div>

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