Compare data from one hour ago with current

[RedRobin132]

Hello!
I have a project where i collect the water level of a river with a sensor. When a predefined height is surpassed, the node red flow send a push message to my phone. Now i want to also compare the current level with the one, i detected on hour ago, so i can see the development over time. Is there a way i can buffer the collected data and compare it? New Data is collected every 10 Minutes.

Thanks in advance!
Robin

[E1cid]

Hi and welcome.

You can use context storage to store data for use later.
One simple way would be store the new data in an array.
Set new data to array[6] and then delete array[0]. This would result in a 6 element array. With array[0] holding the reading from an hour ago, and array[5] holding the newest.
e.g.

[{"id":"9dc7bc361d7f57e2","type":"inject","z":"b779de97.b1b46","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":140,"y":4840,"wires":[["af9dc0530e9f3f77"]]},{"id":"af9dc0530e9f3f77","type":"change","z":"b779de97.b1b46","name":"","rules":[{"t":"set","p":"sensor_data[6]","pt":"flow","to":"payload","tot":"msg"},{"t":"delete","p":"sensor_data[0]","pt":"flow"},{"t":"set","p":"payload","pt":"msg","to":"sensor_data","tot":"flow"}],"action":"","property":"","from":"","to":"","reg":false,"x":300,"y":4840,"wires":[["06aabbd7aa405c1f"]]},{"id":"06aabbd7aa405c1f","type":"debug","z":"b779de97.b1b46","name":"debug 2483","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":470,"y":4840,"wires":[]}]

How to import/export a flow

[jbudd]

@RedRobin132

Now i want to also compare the current level with the one, i detected on hour ago, so i can see the development over time. Is there a way i can buffer the collected data and compare it?

You could also use a database to store the data. SQLite might be appropriate, or MySQL.
That way it's available if you decide you want to correlate the trend with rainfall records, etc.

[RedRobin132]

Thank you both for your answers!
I think i will use both. The context storage for the problem i explained above and the database for future use.