JSON Data From Soil Moisture to Chart

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1

Hi,

I have a soil mositure data logger, I am able to extract JSON data via an API function which returns the following format:

[{"t":"2020-06-10T13:20:16.000Z","v":8.776,"ch":5},
{"t":"2020-06-10T13:18:00.000Z","v":0.508,"ch":3},
{"t":"2020-06-10T13:18:00.000Z","v":2.293,"ch":2},
{"t":"2020-06-10T13:18:00.000Z","v":0.45,"ch":4},
{"t":"2020-06-10T13:18:00.000Z","v":0.322,"ch":1},
{"t":"2020-06-10T12:20:16.000Z","v":8.794,"ch":5},
{"t":"2020-06-10T12:18:00.000Z","v":2.297,"ch":2},
{"t":"2020-06-10T12:18:00.000Z","v":0.443,"ch":4},
{"t":"2020-06-10T12:18:00.000Z","v":0.321,"ch":1},
{"t":"2020-06-10T12:18:00.000Z","v":0.501,"ch":3},
{"t":"2020-06-10T11:20:17.000Z","v":8.794,"ch":5},
{"t":"2020-06-10T11:18:00.000Z","v":2.298,"ch":2},
{"t":"2020-06-10T11:18:00.000Z","v":0.434,"ch":4},
{"t":"2020-06-10T11:18:00.000Z","v":0.318,"ch":1},
{"t":"2020-06-10T11:18:00.000Z","v":0.49,"ch":3},
{"t":"2020-06-10T10:20:16.000Z","v":8.794,"ch":5},
{"t":"2020-06-10T10:18:00.000Z","v":2.297,"ch":2},
{"t":"2020-06-10T10:18:00.000Z","v":0.437,"ch":4},
{"t":"2020-06-10T10:18:00.000Z","v":0.319,"ch":1},
{"t":"2020-06-10T10:18:00.000Z","v":0.486,"ch":3},
{"t":"2020-06-10T09:20:16.000Z","v":8.811,"ch":5},
{"t":"2020-06-10T09:18:00.000Z","v":0.458,"ch":4},
{"t":"2020-06-10T09:18:00.000Z","v":0.321,"ch":1},
{"t":"2020-06-10T09:18:00.000Z","v":0.502,"ch":3},
{"t":"2020-06-10T09:18:00.000Z","v":2.296,"ch":2},
{"t":"2020-06-10T08:20:16.000Z","v":8.811,"ch":5},
{"t":"2020-06-10T08:18:00.000Z","v":0.501,"ch":4},
{"t":"2020-06-10T08:18:00.000Z","v":0.327,"ch":1},
{"t":"2020-06-10T08:18:00.000Z","v":0.539,"ch":3},
{"t":"2020-06-10T08:18:00.000Z","v":2.294,"ch":2}]

I would like to chart the "v" value (voltage) against the time, "t". Each "ch" is a sperate moisture sensor and I would like to show these all the same chart. I am just struggling to get the data structure correct to flow into the chart node, can anyone give me some pointers?

Thanks Very Much

2

The simplest way is just to split the data then move the properties around a little to look like "live" data being injected.

[{"id":"14680093.15867f","type":"inject","z":"d1e29928.8fa058","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":160,"y":1420,"wires":[["8bfdb1d0.cfe"]]},{"id":"8bfdb1d0.cfe","type":"function","z":"d1e29928.8fa058","name":"Example data","func":"msg.payload = [{\"t\":\"2020-06-10T13:20:16.000Z\",\"v\":8.776,\"ch\":5},\n{\"t\":\"2020-06-10T13:18:00.000Z\",\"v\":0.508,\"ch\":3},\n{\"t\":\"2020-06-10T13:18:00.000Z\",\"v\":2.293,\"ch\":2},\n{\"t\":\"2020-06-10T13:18:00.000Z\",\"v\":0.45,\"ch\":4},\n{\"t\":\"2020-06-10T13:18:00.000Z\",\"v\":0.322,\"ch\":1},\n{\"t\":\"2020-06-10T12:20:16.000Z\",\"v\":8.794,\"ch\":5},\n{\"t\":\"2020-06-10T12:18:00.000Z\",\"v\":2.297,\"ch\":2},\n{\"t\":\"2020-06-10T12:18:00.000Z\",\"v\":0.443,\"ch\":4},\n{\"t\":\"2020-06-10T12:18:00.000Z\",\"v\":0.321,\"ch\":1},\n{\"t\":\"2020-06-10T12:18:00.000Z\",\"v\":0.501,\"ch\":3},\n{\"t\":\"2020-06-10T11:20:17.000Z\",\"v\":8.794,\"ch\":5},\n{\"t\":\"2020-06-10T11:18:00.000Z\",\"v\":2.298,\"ch\":2},\n{\"t\":\"2020-06-10T11:18:00.000Z\",\"v\":0.434,\"ch\":4},\n{\"t\":\"2020-06-10T11:18:00.000Z\",\"v\":0.318,\"ch\":1},\n{\"t\":\"2020-06-10T11:18:00.000Z\",\"v\":0.49,\"ch\":3},\n{\"t\":\"2020-06-10T10:20:16.000Z\",\"v\":8.794,\"ch\":5},\n{\"t\":\"2020-06-10T10:18:00.000Z\",\"v\":2.297,\"ch\":2},\n{\"t\":\"2020-06-10T10:18:00.000Z\",\"v\":0.437,\"ch\":4},\n{\"t\":\"2020-06-10T10:18:00.000Z\",\"v\":0.319,\"ch\":1},\n{\"t\":\"2020-06-10T10:18:00.000Z\",\"v\":0.486,\"ch\":3},\n{\"t\":\"2020-06-10T09:20:16.000Z\",\"v\":8.811,\"ch\":5},\n{\"t\":\"2020-06-10T09:18:00.000Z\",\"v\":0.458,\"ch\":4},\n{\"t\":\"2020-06-10T09:18:00.000Z\",\"v\":0.321,\"ch\":1},\n{\"t\":\"2020-06-10T09:18:00.000Z\",\"v\":0.502,\"ch\":3},\n{\"t\":\"2020-06-10T09:18:00.000Z\",\"v\":2.296,\"ch\":2},\n{\"t\":\"2020-06-10T08:20:16.000Z\",\"v\":8.811,\"ch\":5},\n{\"t\":\"2020-06-10T08:18:00.000Z\",\"v\":0.501,\"ch\":4},\n{\"t\":\"2020-06-10T08:18:00.000Z\",\"v\":0.327,\"ch\":1},\n{\"t\":\"2020-06-10T08:18:00.000Z\",\"v\":0.539,\"ch\":3},\n{\"t\":\"2020-06-10T08:18:00.000Z\",\"v\":2.294,\"ch\":2}];\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":320,"y":1420,"wires":[["c99c699d.b9dcc8"]]},{"id":"c99c699d.b9dcc8","type":"split","z":"d1e29928.8fa058","name":"","splt":"\\n","spltType":"str","arraySplt":1,"arraySpltType":"len","stream":false,"addname":"","x":490,"y":1420,"wires":[["796742c6.3d432c"]]},{"id":"796742c6.3d432c","type":"change","z":"d1e29928.8fa058","name":"","rules":[{"t":"set","p":"topic","pt":"msg","to":"payload.ch","tot":"msg"},{"t":"set","p":"timestamp","pt":"msg","to":"payload.t","tot":"msg"},{"t":"move","p":"payload.v","pt":"msg","to":"payload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":660,"y":1420,"wires":[["29af209.92794e"]]},{"id":"29af209.92794e","type":"ui_chart","z":"d1e29928.8fa058","name":"","group":"6bbc8006.c17af","order":0,"width":0,"height":0,"label":"chart","chartType":"line","legend":"false","xformat":"HH:mm:ss","interpolate":"linear","nodata":"","dot":false,"ymin":"","ymax":"","removeOlder":1,"removeOlderPoints":"","removeOlderUnit":"86400","cutout":0,"useOneColor":false,"useUTC":false,"colors":["#1f77b4","#aec7e8","#ff7f0e","#2ca02c","#98df8a","#d62728","#ff9896","#9467bd","#c5b0d5"],"useOldStyle":false,"outputs":1,"x":830,"y":1420,"wires":[[]]},{"id":"6bbc8006.c17af","type":"ui_group","z":"","name":"Switch","tab":"3f2ebb62.3fc404","order":1,"disp":true,"width":"6","collapse":false},{"id":"3f2ebb62.3fc404","type":"ui_tab","z":"d1e29928.8fa058","name":"Home","icon":"fa-tint","order":1,"disabled":false,"hidden":false}]
3

Thanks very much! If I wanted to pull out some topics and display these on a different chart would it be a case of using another split and a rule the specific "ch" numbers required?

4

Probably a switch node but yes.

5

Awesome thanks.

Might be pushing my luck, but what sort of methodology would you use to retrieve the same data format on a time basis and store this data for display and historical tracking?

I am thinking to store the data in a csv and publish that to a webpage chart, but maybe there is a better way?

Cheers

6

Hi
I have similar temperature data and use an InfluxDB node to store this in an InfluxDb database which is designed for time series data. You can then use Grafana as a multi user dashboard to view the data. It may sound complex, but there are plenty of resources and it can be installed on a pi or other hardware. I have a number of these and they work great

7

This is what I used to get started

8

Thanks for the suggestion, I'll check it out :+1:

9

Or you could just reformat the data from the chart into a csv file. Here is an example function that shoudl work

[{"id":"247ee957.a25736","type":"debug","z":"d1e29928.8fa058","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":790,"y":1560,"wires":[]},{"id":"29269901.d23a06","type":"function","z":"d1e29928.8fa058","name":"Chart to CSV","func":"var d = msg.payload[0];\nvar cols = d.series;\nvar series = d.data;\nvar list = {};\n// iterate over all the series\nfor (var i=0; i<cols.length; i++) {\n    // and each data point\n    for (var j=0; j<series[i].length; j++) {\n        // create a new timestamped row if needed\n        if (!list[series[i][j].x]) { list[series[i][j].x] = new Array(d.series.length).fill('') }\n        // otherwise assign each datapoint to that timestamped row\n        list[series[i][j].x][i] = series[i][j].y; \n    }\n}\n\n// create a header line for csv\nvar res = [\"timestamp,\"+cols.join(',')];\n\nvar ordered = {};\n// sort the teimstamped rows into timestamp order\nObject.keys(list).sort().forEach(function(key) { \n    ordered[key] = list[key]; \n    // add the timestampt o the start of the row\n    ordered[key].unshift(parseInt(key));\n    // push them out as a comma separated string\n    res.push(ordered[key].join(','));\n});\n\n// finally join the rows as lines to complete the csv file\nmsg.payload = res.join(\"\\n\");\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":230,"y":1500,"wires":[["6da38900.fd0c48"]]},{"id":"6da38900.fd0c48","type":"trigger","z":"d1e29928.8fa058","name":"","op1":"","op2":"","op1type":"nul","op2type":"payl","duration":"250","extend":true,"units":"ms","reset":"","bytopic":"all","topic":"topic","outputs":1,"x":500,"y":1500,"wires":[["247ee957.a25736","3df76c65.9b73a4"]]},{"id":"3df76c65.9b73a4","type":"file","z":"d1e29928.8fa058","name":"","filename":"/tmp/mychart.csv","appendNewline":true,"createDir":false,"overwriteFile":"true","encoding":"none","x":810,"y":1500,"wires":[[]]}]
10

Thanks very much, I'll take a look at it and see how I go :hugs:

11

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