How to compute and aggregate energy production
Latest activity Reply by Christopher Stapels
on 18 Nov 2022
Dear Community,
I'm new on ThingSpeak for nearly 4 weeks and I'm struggling to compute some MATLAB data. Mostly because I don't know the syntax.
I have a hourly graph of solar production in kW, I'm taking a sample every 20 seconds, and I would like to aggregate the data on a daily basis in kWh.
I guess I need to select the last 7 days of data using some thingsread function, add the data into an array and compute the daily data into an average/sum ... As you can see, I mostly got the mechanics but I'm struggling to create the car ;) Is there anyone kind enough to assist me ?
Thansk a lot !
10 Comments
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Here it is in two glorious lines. Ive done it using the traffic monitor channel, since it posts data every 15 seconds, you can't read 7 days in one try.
myData=thingSpeakRead(38629,'numdays',2,'outputformat','timetable');
newData=retime(myData,'hourly','sum');
Ok, so I gave it a try but without luck :
Here is the code section :
%% Read Data %%
[data, time] = thingSpeakRead(readChannelID, 'Field', fieldID1, 'NumDays', 2, 'ReadKey', readAPIKey);
newData=retime(data,'hourly','sum');
%% Visualize Data %%
plot(time, newData);
title("Last 2 days Aggregation");
xlabel("Time");
ylabel("Production (Wh)");
I'm having this error :
Incorrect number or types of inputs or outputs for function 'retime'.
Error in aggregate (line 21)
newData=retime(data,'hourly','sum');
In case of you wonder, Line 21 is where retime is used.
Look at what else is different about the code I gave you, especially in the first line.
I understood, I'm using an array with 2 dimensions ? right ?
I'm sorry I'm discovering this language...
Sure, welcome to MATLAB. Also look the the name, value pairs I used at the end to get a timetable output. The retime function needs a timetable to act on. You can see those requirements in the doc. MATLAB has famously good doc.
I'm sorry but I'm still not able to do anything :-/
Please show me what you tried and what result you are getting. Here is some updated code.
myData=thingSpeakRead(readChannelID,'numdays',2,'outputformat','timetable'...
,'ReadKey', readAPIKey);
newData=retime(myData,'hourly','sum');
%% Visualize Data %%
plot(newData.Timestamps, newData.(1));
title("Hourly Aggregation");
xlabel("Time");
ylabel("Production (Wh)");
Hi Christopher,
Thanks a lot. I know what's hapening ... Matlab is too powerful ;)
So, I have the data plot now, how can I geet a full week ? I can seemax 3 days.
I know you're stating above I cannot see 7 days in one try, can you elaborate on that ? Since we are aggregating data now, we should have less data in one go ?
Can you try the MATLAB onramp? Its really helpful to get going. If you still have troubles after that, consider starting a new thread on MATLAB answers.
Wow ....
Ok let me try on my side and I'll let you know what I came up with !
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