# Signal and Image Processing

**URL:** https://discourse.julialang.org/c/domain/dsp/26.md?page=4

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**Page:** 5

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## [Ridgelets, Shapelets, Curvelets, Radon Transform etc?](https://discourse.julialang.org/t/ridgelets-shapelets-curvelets-radon-transform-etc/45042)

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**Author:** [@anon92994695](https://discourse.julialang.org/u/anon92994695)\
**Replies:** 1\
**Last updated:** [August 10, 2021, 3:48pm UTC](https://discourse.julialang.org/t/ridgelets-shapelets-curvelets-radon-transform-etc/45042 "2021-08-10T15:48:22Z")

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Anyone know of efforts in Julia to do these fancy \*-let type DSP operations? I was able to find one repository(https://github.com/NFFT/nfft), but it’s a C effort with only a partial Julia interface(it seems)? Whoever i…

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## [DSP.jl power spectra normalization](https://discourse.julialang.org/t/dsp-jl-power-spectra-normalization/26162)

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**Author:** [@Marco-Congedo](https://discourse.julialang.org/u/Marco-Congedo)\
**Replies:** 4\
**Last updated:** [August 1, 2021, 2:48pm UTC](https://discourse.julialang.org/t/dsp-jl-power-spectra-normalization/26162 "2021-08-01T14:48:41Z")

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Can anyone explain the rationale behind the FFT normalization done in DSP.jl, for instance in the periodogram function ? Here below is the concerned code of the fft2pow! function, which computes the power spectra. I am…

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## [Inverse of Cross Correlation?](https://discourse.julialang.org/t/inverse-of-cross-correlation/64357)

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**Author:** [@marianoarnaiz](https://discourse.julialang.org/u/marianoarnaiz)\
**Replies:** 17\
**Last updated:** [July 14, 2021, 7:28pm UTC](https://discourse.julialang.org/t/inverse-of-cross-correlation/64357 "2021-07-14T19:28:33Z")

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Hi all. I have a signal that is a cross correlation between to signals: X=crosscor(A,B) But in my case I get X and I can compute B… any idea how to make the inverse of the cross correlation so that I get: A=icrosscor…

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## [IFFT function in julia](https://discourse.julialang.org/t/ifft-function-in-julia/63454)

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**Author:** [@juls](https://discourse.julialang.org/u/juls)\
**Replies:** 7\
**Last updated:** [June 23, 2021, 7:56pm UTC](https://discourse.julialang.org/t/ifft-function-in-julia/63454 "2021-06-23T19:56:33Z")

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I am trying to implement the below matrix computation from matlab in julia. But the ifft function gives different output than obtained in matlab a = zeros(5,10); for i = 1:5 a(i,:) = ifft((c(i,:).\*(d))); end w…

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## [Getting different output for fft function in julia and matlab](https://discourse.julialang.org/t/getting-different-output-for-fft-function-in-julia-and-matlab/63349)

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**Author:** [@juls](https://discourse.julialang.org/u/juls)\
**Replies:** 4\
**Last updated:** [June 22, 2021, 9:42am UTC](https://discourse.julialang.org/t/getting-different-output-for-fft-function-in-julia-and-matlab/63349 "2021-06-22T09:42:29Z")

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In JULIA, 2×5 Array{Float64,2}: 0.801514 1.21987 1.1503 1.18761 1.2485 0.807469 1.22325 1.14981 1.1877 1.24861 when fft function from FFTW.jl on the above array gives output: 2×5 Array{Complex{Float64},2}: …

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## [How to determine whenever there's an oscillation](https://discourse.julialang.org/t/how-to-determine-whenever-theres-an-oscillation/48936)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 23\
**Last updated:** [April 26, 2021, 2:22pm UTC](https://discourse.julialang.org/t/how-to-determine-whenever-theres-an-oscillation/48936 "2021-04-26T14:22:53Z")

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Hello, I am looking for some advice: I have a system that I am investigating, and I am trying to determine for which parameter values it exhibits which behaviours. There are several different ones, but a typical is that…

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## [Filter design: MATLAB firls (Least-squares linear-phase FIR filter design) alternative?](https://discourse.julialang.org/t/filter-design-matlab-firls-least-squares-linear-phase-fir-filter-design-alternative/45249)

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**Author:** [@ElectronicTeaCup](https://discourse.julialang.org/u/ElectronicTeaCup)\
**Replies:** 17\
**Last updated:** [April 22, 2021, 6:49pm UTC](https://discourse.julialang.org/t/filter-design-matlab-firls-least-squares-linear-phase-fir-filter-design-alternative/45249 "2021-04-22T18:49:53Z")

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Hi! I am going through a MATLAB based textbook for time frequency analysis of Neural data (MEG/EEG time series data) and got to a chapter which goes through filter construction. It’s primarily going over the usage of the…

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## [Frequency Response Functions (FRF) in Julia](https://discourse.julialang.org/t/frequency-response-functions-frf-in-julia/57900)

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**Author:** [@Eggy](https://discourse.julialang.org/u/Eggy)\
**Replies:** 49\
**Last updated:** [April 15, 2021, 3:36am UTC](https://discourse.julialang.org/t/frequency-response-functions-frf-in-julia/57900 "2021-04-15T03:36:24Z")

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I have followed Julia for a while, but I am now just getting into using it more. I have collected data from performing what’s known as an roving hammer test with my accelerometer and an non-instrumented hammer to derive …

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## [Upsampling or downsampling sample data of two sensors to match](https://discourse.julialang.org/t/upsampling-or-downsampling-sample-data-of-two-sensors-to-match/58937)

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**Author:** [@Eggy](https://discourse.julialang.org/u/Eggy)\
**Replies:** 2\
**Last updated:** [April 9, 2021, 7:43pm UTC](https://discourse.julialang.org/t/upsampling-or-downsampling-sample-data-of-two-sensors-to-match/58937 "2021-04-09T19:43:18Z")

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I used two accelerometers to collect data, but forgot to check and put them at the same sample rate; they went back to their defaults. One was sampling at 256 Hz and the other was sampling at 100 Hz. I am looking for fre…

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## [\`plan\_rfft\` together used with \`mul!\` and \`@view\` complains about wrong-strides-output](https://discourse.julialang.org/t/plan-rfft-together-used-with-mul-and-view-complains-about-wrong-strides-output/58215)

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**Author:** [@roflmaostc](https://discourse.julialang.org/u/roflmaostc)\
**Replies:** 24\
**Last updated:** [March 30, 2021, 10:24pm UTC](https://discourse.julialang.org/t/plan-rfft-together-used-with-mul-and-view-complains-about-wrong-strides-output/58215 "2021-03-30T22:24:47Z")

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Hey, initially I wanted to have rfft! but since it doesn’t exist, I tried the workaround mentioned in this discourse discussion. However, mul! complains when used with a plan\_rfft generated matrix: using LinearAlgebra…

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## [Spectral acceleration](https://discourse.julialang.org/t/spectral-acceleration/56895)

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**Author:** [@Frederic\_Gilt](https://discourse.julialang.org/u/Frederic_Gilt)\
**Replies:** 0\
**Last updated:** [March 10, 2021, 3:52pm UTC](https://discourse.julialang.org/t/spectral-acceleration/56895 "2021-03-10T15:52:50Z")

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Dear community, I have accelerations ai during each time step ti for a given time range \[ai ti\] as raw datas and was wondering if Julia has some already prepared spectral acceleration tool… If not I have a pseudo-code …

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## [How to use Fourier Filter on Complex Data](https://discourse.julialang.org/t/how-to-use-fourier-filter-on-complex-data/54967)

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**Author:** [@mdsa3d](https://discourse.julialang.org/u/mdsa3d)\
**Replies:** 8\
**Last updated:** [March 4, 2021, 2:16am UTC](https://discourse.julialang.org/t/how-to-use-fourier-filter-on-complex-data/54967 "2021-03-04T02:16:06Z")

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I would like to know, how may I filter or separate this complex function into its simpler sub-functions (something like fourier filter). Example I have a noisy dataset: x = 1:1:10 y = \[-1,5,0,2,-7,1,6,9,-2,3\] If I wou…

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## [Mirroring signal before fft](https://discourse.julialang.org/t/mirroring-signal-before-fft/55749)

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**Author:** [@chaseleslie](https://discourse.julialang.org/u/chaseleslie)\
**Replies:** 3\
**Last updated:** [February 22, 2021, 3:45am UTC](https://discourse.julialang.org/t/mirroring-signal-before-fft/55749 "2021-02-22T03:45:35Z")

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I have inherited some code that mirrors a signal before taking the discrete Fourier transform of it, essentially like this: signal = vcat(reverse(signal), signal) # windowing and padding operations ... sig = fft(signal)…

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## [DSP Filter application](https://discourse.julialang.org/t/dsp-filter-application/55156)

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**Author:** [@roble](https://discourse.julialang.org/u/roble)\
**Replies:** 13\
**Last updated:** [February 17, 2021, 4:28pm UTC](https://discourse.julialang.org/t/dsp-filter-application/55156 "2021-02-17T16:28:45Z")

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Hi, I am trying to use the filt(f, x\[, si\]) function from the DSP.jl module. My raw data looks like this: On this data I apply a lowpass filter: df.data\_raw # my raw data w0 = 1/120 # cutoff frequency df.data\_lp= …

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## [Impulse response of Butterworth filter](https://discourse.julialang.org/t/impulse-response-of-butterworth-filter/51543)

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**Author:** [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)\
**Replies:** 4\
**Last updated:** [December 17, 2020, 5:31pm UTC](https://discourse.julialang.org/t/impulse-response-of-butterworth-filter/51543 "2020-12-17T17:31:54Z")

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In the following code example, a 6th-order Butterworth filter is defined over 4-50 Hz and the frequency response plotted. How to use DSP.jl to compute the corresponding zero-phase filter time response? Using filt(fil,ht…

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## [Calculating Breaths Per Minute from Video Data](https://discourse.julialang.org/t/calculating-breaths-per-minute-from-video-data/51582)

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**Author:** [@RodBiren](https://discourse.julialang.org/u/RodBiren)\
**Replies:** 9\
**Last updated:** [December 10, 2020, 6:20pm UTC](https://discourse.julialang.org/t/calculating-breaths-per-minute-from-video-data/51582 "2020-12-10T18:20:32Z")

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I have been able to process video data of myself sleeping using a Wyze camera to produce fairly solid data that I would like to use to calculate breaths per minute.The actual calculation is trivial. I calculate the perce…

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## [Fft() function does not return the correct analytic result](https://discourse.julialang.org/t/fft-function-does-not-return-the-correct-analytic-result/50644)

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**Author:** [@tiago](https://discourse.julialang.org/u/tiago)\
**Replies:** 5\
**Last updated:** [November 26, 2020, 7:21pm UTC](https://discourse.julialang.org/t/fft-function-does-not-return-the-correct-analytic-result/50644 "2020-11-26T19:21:58Z")

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Hello, currently I’m having issues understanding how to perform with success a Fourier Transformation using the fft() function of the fftw.jl package. Let’s pick the step function: using FFTW, Plots x = range(-5,stop=5…

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## [Not sure how to apply a filter](https://discourse.julialang.org/t/not-sure-how-to-apply-a-filter/50265)

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**Author:** [@klaff](https://discourse.julialang.org/u/klaff)\
**Replies:** 7\
**Last updated:** [November 18, 2020, 4:11pm UTC](https://discourse.julialang.org/t/not-sure-how-to-apply-a-filter/50265 "2020-11-18T16:11:53Z")

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I’ve constructed a filter as follows: filter1 = let f1 = 6.31 f2 = 1258.9 Q1 = 0.71 f3 = 15.915 f4 = 15.915 Q2 = 0.64 SecondOrderSections(\[ Biquad(4π^2\*f2^2,0.0,0.0,2π\*f1/Q1, 4π^2\*f1^2), Biquad(0.0,0.0,1.0,…

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## [Obtain Envelope](https://discourse.julialang.org/t/obtain-envelope/46643)

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**Author:** [@carlomontec](https://discourse.julialang.org/u/carlomontec)\
**Replies:** 13\
**Last updated:** [November 16, 2020, 6:55pm UTC](https://discourse.julialang.org/t/obtain-envelope/46643 "2020-11-16T18:55:58Z")

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Hello, is there any function or library to obtain the envelope of a signal ? Thank you all.

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## [Bug detected in deconvolution operation deconv()](https://discourse.julialang.org/t/bug-detected-in-deconvolution-operation-deconv/49546)

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**Author:** [@iamsuddhasattwa](https://discourse.julialang.org/u/iamsuddhasattwa)\
**Replies:** 4\
**Last updated:** [November 10, 2020, 9:34pm UTC](https://discourse.julialang.org/t/bug-detected-in-deconvolution-operation-deconv/49546 "2020-11-10T21:34:17Z")

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The DSP package contains some routines very vital and basic to Fourier analysis. However the simple deconvultion operation is not working. Consider the following simple code using DSP; a = zeros( Float64, 5); a\[3\]=10; b…

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## [What scaling applies to the irfft (inverse fast fourier transform - FFTW.jl package)](https://discourse.julialang.org/t/what-scaling-applies-to-the-irfft-inverse-fast-fourier-transform-fftw-jl-package/47476)

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**Author:** [@jleman](https://discourse.julialang.org/u/jleman)\
**Replies:** 4\
**Last updated:** [September 29, 2020, 5:28pm UTC](https://discourse.julialang.org/t/what-scaling-applies-to-the-irfft-inverse-fast-fourier-transform-fftw-jl-package/47476 "2020-09-29T17:28:37Z")

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I am trying to understand scaling of the irfft function of the FFTW.jl package. I have a function that defines a continuous frequency domain signal (in radians). The complex portion of the signal has odd symmetry and t…

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## [Suggestions for playing music from real-time data generated in Julia](https://discourse.julialang.org/t/suggestions-for-playing-music-from-real-time-data-generated-in-julia/46448)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 4\
**Last updated:** [September 12, 2020, 1:59pm UTC](https://discourse.julialang.org/t/suggestions-for-playing-music-from-real-time-data-generated-in-julia/46448 "2020-09-12T13:59:21Z")

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A little project I have in mind requires making data in real time (well, maybe 100 times a second at most) that is used to output music in real time. Details are scant because I haven’t really done anything yet, I’m tryi…

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## [Obtain frequency response from digital filter with DSP.jl](https://discourse.julialang.org/t/obtain-frequency-response-from-digital-filter-with-dsp-jl/44618)

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**Author:** [@marcpabst](https://discourse.julialang.org/u/marcpabst)\
**Replies:** 4\
**Last updated:** [September 2, 2020, 4:59am UTC](https://discourse.julialang.org/t/obtain-frequency-response-from-digital-filter-with-dsp-jl/44618 "2020-09-02T04:59:33Z")

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Hi, I have a simple and potentially very stupid question. I use DSP.jl to construct a filter via digitalfilter(), which leaves me with a filter kernel I can apply to my signal. If I wanted to take a look at the respons…

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## [Creating a video from a stack of Images](https://discourse.julialang.org/t/creating-a-video-from-a-stack-of-images/646)

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**Author:** [@vchuravy](https://discourse.julialang.org/u/vchuravy)\
**Replies:** 11\
**Last updated:** [August 26, 2020, 12:51am UTC](https://discourse.julialang.org/t/creating-a-video-from-a-stack-of-images/646 "2020-08-26T00:51:07Z")

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VideoIO.jl only seems to have the capabilities of reading in video with ffmpeg. I couldn’t find any options to create a Video so I was wondering if I am missing something. I know @sdanisch is exporting to png files fir…

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## [Failed to obtain the correct phase?](https://discourse.julialang.org/t/failed-to-obtain-the-correct-phase/45350)

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**Author:** [@tomtom](https://discourse.julialang.org/u/tomtom)\
**Replies:** 3\
**Last updated:** [August 24, 2020, 2:07pm UTC](https://discourse.julialang.org/t/failed-to-obtain-the-correct-phase/45350 "2020-08-24T14:07:58Z")

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I’m trying to extract the amplitude, period and phase of a pure sinusoidal signal: using FFTW a = 3cos.(2π/17 .\* (1:4096) .+ 0.2); fa = fft(a)\[1:2048\]; fam = abs.(fa); famfm = findmax(fam) julia\> famfm = findmax(fam) (…

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## [How to resize a very large array or image without changing its number type](https://discourse.julialang.org/t/how-to-resize-a-very-large-array-or-image-without-changing-its-number-type/43936)

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**Author:** [@rio](https://discourse.julialang.org/u/rio)\
**Replies:** 1\
**Last updated:** [July 30, 2020, 8:51am UTC](https://discourse.julialang.org/t/how-to-resize-a-very-large-array-or-image-without-changing-its-number-type/43936 "2020-07-30T08:51:14Z")

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Hi, I would like to resize an array (or perhaps an image) and get a result of the same type. For instance, in my code below: N = 10 img = rand(Int8,N,N,3) img = imresize(img,ratio=(0.7, 0.7, 1)) the outupt img change…

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## [How to use dilate in Julia](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241)

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**Author:** [@sudo](https://discourse.julialang.org/u/sudo)\
**Replies:** 9\
**Last updated:** [July 19, 2020, 1:58pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241 "2020-07-19T13:58:05Z")

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Hi! I am looking for something similar to python’s dilation function in skimage.morphology. I want to achieve precisely the following functionality: \>\>\> import numpy as np \>\>\> from skimage.morphology import dilation \>\>\> …

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## [Fourier transform freezes Julia](https://discourse.julialang.org/t/fourier-transform-freezes-julia/38771)

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**Author:** [@Martijn-R](https://discourse.julialang.org/u/Martijn-R)\
**Replies:** 5\
**Last updated:** [July 3, 2020, 12:56pm UTC](https://discourse.julialang.org/t/fourier-transform-freezes-julia/38771 "2020-07-03T12:56:30Z")

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I am processing an audio sample (about 20minutes long) in small parts of several seconds. At the moment my code freezes every now and then. The example below is a bit silly but is a minimal ‘working’ example which oft…

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## [Julia vs GNU Octave for plot fitting / finding peaks](https://discourse.julialang.org/t/julia-vs-gnu-octave-for-plot-fitting-finding-peaks/42237)

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**Author:** [@doronbehar](https://discourse.julialang.org/u/doronbehar)\
**Replies:** 16\
**Last updated:** [July 1, 2020, 7:33am UTC](https://discourse.julialang.org/t/julia-vs-gnu-octave-for-plot-fitting-finding-peaks/42237 "2020-07-01T07:33:34Z")

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I’m currently using GNU octave to fit a simple cosine with a phase to many data sets stored in text files. For most data sets, the fit works well, but for some others, it doesn’t. I’m wondering whether I’d be able to get…

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## [Dynamic Time Warping in Julia](https://discourse.julialang.org/t/dynamic-time-warping-in-julia/13426)

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**Author:** [@Moses](https://discourse.julialang.org/u/Moses)\
**Replies:** 7\
**Last updated:** [April 24, 2020, 10:35am UTC](https://discourse.julialang.org/t/dynamic-time-warping-in-julia/13426 "2020-04-24T10:35:42Z")

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Hello everybody. I hope, I am in the right domain for this question. I am looking for an implemantation of dynamic time warping in julia. Obviously, there has been some work on this already: here and here. However, bot…

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