Timeline for How can I take a fixed number of bins after N-point DFT when N is unknown?
Current License: CC BY-SA 3.0
12 events
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| Sep 19, 2017 at 1:39 | history | tweeted | twitter.com/StackSignals/status/909955052491689989 | ||
| Sep 18, 2017 at 22:48 | answer | added | Dave Kielpinski | timeline score: 0 | |
| Sep 18, 2017 at 12:26 | comment | added | Olli Niemitalo | About interpolation of the frequency data (not saying it is the right path to take), see: Question: Interpolation of magnitude of discrete Fourier transform (DFT) | |
| Sep 18, 2017 at 12:06 | comment | added | ishouldknowtheanswerbutidont |
It's quite simple. The Fourier coefficients go from X[1] through X[N/2 + 1], so I just scale the sequence of points 0..50 accordingly and call interp1 to query X on the scaled points, then add 1 because Matlab index from 1. But again, I am not required to use interp1 or anything similar. I just want to estimate the frequency content at specific bins, regardless of the length of the series.
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| Sep 18, 2017 at 12:02 | history | edited | ishouldknowtheanswerbutidont | CC BY-SA 3.0 |
added 139 characters in body; edited tags
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| Sep 15, 2017 at 18:18 | comment | added | Dave Kielpinski |
I can probably answer your question, but it depends on the details of your downsampling procedure. I understand you are using Matlab interp1 but is there more to it? Can you post this part of your code?
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| Sep 15, 2017 at 15:32 | answer | added | user28715 | timeline score: 2 | |
| Sep 15, 2017 at 14:52 | comment | added | ishouldknowtheanswerbutidont | Thanks for that question. I am indeed downsampling, but unintentionally. Effectively, when I can drop every other bin, that's what Matlab is doing. Otherwise it averages certain bins and drops others. Looks even worse than what I thought I was doing wrong. How should I proceed? | |
| Sep 15, 2017 at 14:51 | history | edited | ishouldknowtheanswerbutidont | CC BY-SA 3.0 |
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| Sep 15, 2017 at 1:29 | comment | added | Dave Kielpinski | Your plots show that you are downsampling or smoothing somehow, not just interpolating. Interpolation always produces more data points. Please clarify this part of your procedure. | |
| Sep 14, 2017 at 15:05 | review | First posts | |||
| Sep 14, 2017 at 15:26 | |||||
| Sep 14, 2017 at 15:00 | history | asked | ishouldknowtheanswerbutidont | CC BY-SA 3.0 |