Sebastian asked . 2021-01-06

How does "pwelch" function assign frequency bins?

I’m giving a timeseries vector with 14600 data points as an input to the “pwelch” function and getting 2049 data points as an output. I’m not sure how to assign these output points to specific frequencies, I need more info on how the averaging/binning works with this function?

matlab , signal , signal processing

Expert Answer

John Williams answered . 2024-05-19 01:33:33

Welch's overlapped segment averaging method reduces the variance in the periodogram by averaging PSD estimates based on segments.
In your case, the signal is 14,600 elements long, so the signal is divided into segments of length 3244 and use the default overlap of 50% or 1622 samples.
In this case the 8 segments have start and end times as follows:
Start points End points
1 3244
1623 4866
3245 6488
4867 8110
6489 9732
8111 11354
9733 12976
11355 14598
Since the segment length is 3244, the help states about the default NFFT value or number of frequency bins:
"If NFFT is specified as empty, NFFT is set to either 256 or the next power of two greater than the length of each section of X, whichever is larger." In this case the next power of two greater than 3244 is 4096.
So, the resulting PSD estimate is obtained by averaging the PSD estimates of the given eight 3244-point segments padded to 4096 points.
The actual frequencies are available as an output from pwelch(). " >> [pxx,w] = pwelch(ts)" returns the normalized frequency vector, w.
They are spaced as (2*pi)/4096 if your do not specify a sampling frequency -- radians/sample. or Fs/4096 if a sampling frequency is specified.
If the  signal is real-valued, then by default we only return the non-negative frequencies, so then you will obtain only 2049 points for the PSD estimate and the frequencies, but the frequency resolution (spacing between DFT bins) is as I described.


Not satisfied with the answer ?? ASK NOW

Frequently Asked Questions

MATLAB offers tools for real-time AI applications, including Simulink for modeling and simulation. It can be used for developing algorithms and control systems for autonomous vehicles, robots, and other real-time AI systems.

MATLAB Online™ provides access to MATLAB® from your web browser. With MATLAB Online, your files are stored on MATLAB Drive™ and are available wherever you go. MATLAB Drive Connector synchronizes your files between your computers and MATLAB Online, providing offline access and eliminating the need to manually upload or download files. You can also run your files from the convenience of your smartphone or tablet by connecting to MathWorks® Cloud through the MATLAB Mobile™ app.

Yes, MATLAB provides tools and frameworks for deep learning, including the Deep Learning Toolbox. You can use MATLAB for tasks like building and training neural networks, image classification, and natural language processing.

MATLAB and Python are both popular choices for AI development. MATLAB is known for its ease of use in mathematical computations and its extensive toolbox for AI and machine learning. Python, on the other hand, has a vast ecosystem of libraries like TensorFlow and PyTorch. The choice depends on your preferences and project requirements.

You can find support, discussion forums, and a community of MATLAB users on the MATLAB website, Matlansolutions forums, and other AI-related online communities. Remember that MATLAB's capabilities in AI and machine learning continue to evolve, so staying updated with the latest features and resources is essential for effective AI development using MATLAB.

Without any hesitation the answer to this question is NO. The service we offer is 100% legal, legitimate and won't make you a cheater. Read and discover exactly what an essay writing service is and how when used correctly, is a valuable teaching aid and no more akin to cheating than a tutor's 'model essay' or the many published essay guides available from your local book shop. You should use the work as a reference and should not hand over the exact copy of it.

Matlabsolutions.com provides guaranteed satisfaction with a commitment to complete the work within time. Combined with our meticulous work ethics and extensive domain experience, We are the ideal partner for all your homework/assignment needs. We pledge to provide 24*7 support to dissolve all your academic doubts. We are composed of 300+ esteemed Matlab and other experts who have been empanelled after extensive research and quality check.

Matlabsolutions.com provides undivided attention to each Matlab assignment order with a methodical approach to solution. Our network span is not restricted to US, UK and Australia rather extends to countries like Singapore, Canada and UAE. Our Matlab assignment help services include Image Processing Assignments, Electrical Engineering Assignments, Matlab homework help, Matlab Research Paper help, Matlab Simulink help. Get your work done at the best price in industry.