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Questions tagged [spectral-density]

63 questions
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Computing a power spectrum

I would like to compute a power spectrum using Python3. From another thread about this topic I got the basic ingredients. I think it should be something like: ps = np.abs(np.fft.fft(x))**2 timeres = t[1]-t[0] freqs = np.fft.fftfreq(x.size,…
user90465
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How to open/read an ENVI file in R

I'm new at using GIS with R and I'm trying to open an ENVI file containing hyperspectral data following the suggestions from this post R how to read ENVI .hdr-file?, but I don't seem to be able to do so. I tried three different approaches but all of…
Adriana Castillo Castillo
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Implementing Matlab's avgpower in Octave?

Folks, Matlab 2007b (7.5.0) has an avgpower function. See here: "The avgpower method uses a rectangle approximation to the integral to calculate the signal's average power using the PSD data stored in the object. "The avgpower method returns the…
dfrankow
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Accessing raw data from annotations without creating epochs

I want to compute PSD of an EEG signal during REM sleep stage. I have a raw EEG signal annotated with sleep stages. The description of my annotations are 'S0, S1, S2, S3, REM'. Is there a way to access the raw signal directly from annotations…
ophelia
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Estimate model order of an autoregressive (AR) model

I am trying to use pmcov() function of MATLAB to calculate power spectral density estimates (PSD) of a discrete time signal 700 ms long with sampling frequency 1000 Hz. This function requires the model order of the autoregressive model used to…
user8020776
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Accessing processed values from FFT

I am attempting to use Lomont FFT in order to return complex numbers to build a spectrogram / spectral density chart using c#. I am having trouble understanding how to return values from the class. Here is the code I have put together thus far which…
Majickal
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Error when doing power spectrum analysis in R

I am trying to do a spectral density analysis with ozone data but have run into the error: Error in ts(tser, frequency = x.fsamp, start = x.start) : 'ts' object must have one or more observations I am not sure what the problem is because it…
user5727
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Multiple PSD in same graph - Matlab

I intend to plot multiple Power Spectral Densities on the same graph. I am using the following to plot the power spectral density for a single signal. hss = dsp.SpectrumAnalyzer('SampleRate', Fs); step(hss,rx); release(hss); However, if I were to…
smyslov
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Change psd plot to display frequency in Hz instead of kHz

In MATLAB I can't seem to figure out how to get the dspdata.psd function to display my power spectral density plot in Hz instead of kHz for the x-axis. If anyone knows a solution it would be greatly appreciated, thank you!
Vincent
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Curve fiting a custom model matlab

I'm trying to fit a model to the curve you see below: I need to find a routine for this problem, so it gives optimized value for these parameters (even when the curve is so noisy). I can find some initial guess for the parameters, but I need…
Mona MK
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Complex cross spectral density

mlab.csd from matplotlib: http://matplotlib.org/api/mlab_api.html#matplotlib.mlab.csd can be used to get real valued cross spectral density. If I want to get the phase information from the spectral density, I need a csd calculation which returns…
umayfindurself
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How does we calculate PSD of a dataset in R

I have a dataset of EEG signals over a period of time and I need to calculate PSD observation of it. In matlab I can calculate the PSD of a signal, for that I have a built in function. Does R have a function to calculate the PSD observation of a…
cppiscute
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Generating Images In Specific Screen Size Densities

I'm building an app with one image file that is used throughout the apps views. I'm a little confused about the information in android.developers in regards to scaling images to the different screen densities in Android: ldpi = 0.75; mdpi = 1.0;…
embersofadyingfire
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spectral coherence of time seires

I have two time series of data, one which is water temperature and the other is air temperature (hourly measurements for one year). Both measurements are taken simultaneously and the vectors are therefore the same size. The command corrcoef…
Emma
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Welch periodogram for turbulence spectrum

I am trying to compute the turbulence density spectrum with a Welch periodogram. The results seem good but I do not manage to find the fluctuation of streamwise velocity that I am supposed to find when computing the integral of the spectrum. Here is…
Martin7
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