Help with DOST - Including Data and Example

[jasonnicholson]

First of all, thank you for posting your software!

The Stockwell Transform is very interesting to me. I use the STFT with a hamming window, and I correct the amplitude so that 1 unit of amplitude in the time domain is 1 unit of amplitude in the frequency domain. A sine/cosine wave has the same amplitude in the STFT at the same frequency. This is much more intuitive for Mechanical Engineers than the actual amplitudes of FFT's, windowed FFT's, etc at a particular frequency. While STFT does work, it is clear that in time-frequency analysis, the STFT is old technology. I want to work with the Stockwell Transform to explore its applications and improvements over the STFT. I want to produce spectrogram-like plots. I want to pull out phase, amplitude, and frequency information from the Stockwell Transform.

Attached is a script and some data. I am trying to plot an amplitude vs time and frequency. The challenges are listed below

• St.dost throws warnings at line 200. The warning is shown below. I am confident when you try to run the script you will see the same thing I did.

  Warning: Integer operands are required for colon operator when used as index. In ST.dost (line 200) In example (line 15)

• ST.rearrangeDost errors out because the size of the matrix output is so large. I think a sparse matrix may work here. I think first calculating the column, row, and values in vectors, and then calling sparse() once should work the best if a sparse matrix is a good fit. If not, we can use some sort of adaptive quad mesh to plot the time-frequency amplitude plot.

  Error using zeros Requested 1617185x1617185 (19485.4GB) array exceeds maximum array size preference. Creation of arrays greater than this limit may take a long time and cause MATLAB to become unresponsive. Error in ST.rearrangeDost (line 374) out = zeros(D, D); Error in example (line 16) X_readableDost = ST.rearrangeDost(X_dost); % This line won't run because of output matrix requires to much memory. Related documentation

Thank you for reading. Good luck.

Example.zip

[luigir86]

Hi Jason, thanks for the questions.

Regarding the first warning: as mentioned in the tutorial the code works for signal of size 2^k. You should pad your signal before calling the dost function with something like this: paddedX = zeros(2^nextpow2(length(x)),1); paddedX(1:length(x)) = x;

Regarding the rearrangeDost function I haven't yet found a solution but I will look into it. Probably your suggestion could work.

Best, Luigi

[jasonnicholson]

Thank you!

[Gray-ly]

Thanks for the share，

Which value can I adjust to change the coefficient of the window function μ and σ， So as to obtain dost with higher resolution？

Thank you for answer. Good luck.