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Fast Fourier transform and moving average in mat lab.
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muunduk@gmail.com
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October 11, 2015 - 1:06 am
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Hey,
I recently joined Thingspeak.com and I want to log voltage and current reading and measure up the 10th harmonic hence I am wondering if anyone knows how to perform the fast Fourier transform of data posted to Thingspeak.com.

I am monitoring a like that expects Dc current only hence I would like to implement a moving average filter if it has any disturbances. Any help or suggestion will be highly appreciated

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akhila

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October 11, 2015 - 8:04 pm
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hi,

You could use MATLAB Analysis app in ThingSpeak to do the fast fourier transform of data.

You would need to read the data from your ThingSpeak channel via ThingSpeakRead API.

Here are links to relevant documentation:

1. MATLAB Analysis: https://thingspeak.com/docs/matlab_analysis#matlab_analysis
2. ThingSpeakRead: https://thingspeak.com/docs/matlab_analysis#thingSpeakRead
3. FFT using MATLAB: http://www.mathworks.com/help/matlab/ref/fft.html

Thanks
Akhila

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muunduk@gmail.com
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October 13, 2015 - 7:40 pm
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Hey akhila

Thanks for this really helped, I managed to read my data and plot a graph of the data in thingspeak by using
thingSpeakPlot(data); but i am not able to do the fft, if you know the syntax on how to perform the fft , please help.

Thanks

Muundu

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Rob Purser
Natick, MA

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October 14, 2015 - 9:41 am
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Hi,

Like Akhila commented earlier, there's a good discussion of how to use the FFT function in MATLAB. See the link she posted. There's also a good discussion here: http://www.mathworks.com/matlabcentral/newsreader/view_thread/27009

Typically, people are really interested in the Power Spectral Density, rather than the true FFT -- the topic above discusses that, and wikipedia has a lot of good information.

-Rob

Senior Development Manager for IoT and Hardware Interfacing for MATLAB at MathWorks.  Visit ThingSpeak.com to explore the IoT Analytic platform that speaks MATLAB made for engineers and scientists.  You can collect, analyze, and act in 5 minutes or less!

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