# Find Power Spectrum and Density

**URL:** <https://discourse.julialang.org/t/find-power-spectrum-and-density/85415>\
**Category:** Signal and Image Processing\
**Tags:** fftw, dsp\
**Created:** [August 6, 2022, 9:06pm UTC](https://discourse.julialang.org/t/find-power-spectrum-and-density/85415 "2022-08-06T21:06:34Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![natgeo-wong](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/natgeo-wong/32/10965_2.png) [@natgeo-wong](https://discourse.julialang.org/u/natgeo-wong)\
**Post date:** [August 6, 2022, 9:06pm UTC](https://discourse.julialang.org/t/find-power-spectrum-and-density/85415/1 "2022-08-06T21:06:34Z")

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Hi! I have a set of time-series data. I’d just like to ask, are there packages available to decompose the signal into the power spectrum and the density/amplitude?

And also, I would like to ask if there is a way to do filtering of the time-series based on frequency as well?

The time-series data would most likely be evenly spaced in time.

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**Author:** ![rafael.guerra](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rafael.guerra/32/216610_2.png) [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)\
**Post date:** [August 6, 2022, 10:19pm UTC](https://discourse.julialang.org/t/find-power-spectrum-and-density/85415/2 "2022-08-06T22:19:27Z")

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DSP.jl should be your first stop for time-series evenly spaced in time.

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**Author:** ![natgeo-wong](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/natgeo-wong/32/10965_2.png) [@natgeo-wong](https://discourse.julialang.org/u/natgeo-wong)\
**Post date:** [August 7, 2022, 12:40am UTC](https://discourse.julialang.org/t/find-power-spectrum-and-density/85415/3 "2022-08-07T00:40:55Z")

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I’ve had a look at DSP.jl, but I do not understand how to use it from the documentation. There is no simple example that shows how to construct `filt`, for example. I do not know what we mean by filter coefficients?

I could do it very easily in MATLAB using FFT, for example, but I’m not sure what the equivalent is here?

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**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [August 7, 2022, 12:48am UTC](https://discourse.julialang.org/t/find-power-spectrum-and-density/85415/4 "2022-08-07T00:48:08Z")

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For FFT look at: [FFT Tutorial | Using the Fast Fourier Transform](https://www.matecdev.com/posts/fft-tutorial.html)

For filter design look at [Filters - filter design and filtering · DSP.jl](https://docs.juliadsp.org/stable/filters/#Filter-design)  
You find some exaples at the end: [Filters - filter design and filtering · DSP.jl](https://docs.juliadsp.org/v0.7/filters/#Examples)

A simple, but outdated tutorial is [A really brief introduction to audio signal processing in Julia | seaandsailor](https://www.seaandsailor.com/audiosp_julia.html) .

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<div class="post-metadata">

**Author:** ![rafael.guerra](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rafael.guerra/32/216610_2.png) [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)\
**Post date:** [August 7, 2022, 5:58am UTC](https://discourse.julialang.org/t/find-power-spectrum-and-density/85415/5 "2022-08-07T05:58:54Z")

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> [@natgeo-wong](#):
>
> There is no simple example that shows how to construct `filt`, for example

If you search here in discourse the tags `dsp` and `fftw` you will find several of them.