Underdetermined systems and compressed sensing [Python]

  Рет қаралды 19,713

Steve Brunton

Steve Brunton

3 жыл бұрын

This video shows how to solve for the sparse solution of an underdetermined system of equations using compressed sensing (code in Python).
Book Website: databookuw.com
Book PDF: databookuw.com/databook.pdf
These lectures follow Chapter 3 from:
"Data-Driven Science and Engineering: Machine Learning, Dynamical Systems, and Control" by Brunton and Kutz
Amazon: www.amazon.com/Data-Driven-Sc...
Brunton Website: eigensteve.com
This video was produced at the University of Washington

Пікірлер: 43
@user-vj9or3hb5j
@user-vj9or3hb5j Жыл бұрын
Love these lectures, thank you!
@fazelpour
@fazelpour 7 ай бұрын
Dear Professor, We cannot thank you enough for sharing your knowledge with us, especially in a way that we, as non-experts, can get it. Your Python codes makes the lessons immediately usable for our daily problems. I wish you would one day, extend it to the numerical solutions for the Maxwell equations to simulate S-parameters for an interconnect structure consisting of power ports.
@jairjuliocc
@jairjuliocc 3 жыл бұрын
It's awesome what you can do with linear algebra. Thank you for the explanation
@Eigensteve
@Eigensteve 3 жыл бұрын
Glad you think so!
@arunrajiitbaero
@arunrajiitbaero 3 жыл бұрын
I wish i have such a lightboard with good acoustics. Simply the best way for teaching theory and math.
@totifroti4515
@totifroti4515 Жыл бұрын
Awesome, brilliant 👏
@MikhailBarabanovA
@MikhailBarabanovA 3 жыл бұрын
Brilliant as always! Thanks!
@Eigensteve
@Eigensteve 3 жыл бұрын
Glad you enjoyed it!
@billybest5276
@billybest5276 3 жыл бұрын
these videos are so good
@Eigensteve
@Eigensteve 3 жыл бұрын
Thanks!
@jorgevargas8458
@jorgevargas8458 2 жыл бұрын
Thank for the lecture, one question: the algorthims that you implemented in python with the L1 norm is called basic pursuit rigth?
@RussStukel
@RussStukel 3 жыл бұрын
Very cool stuff from a TAMS graduate! ha - all the best to you Dr. B.
@Eigensteve
@Eigensteve 3 жыл бұрын
Awesome, thanks Russ!
@leif1075
@leif1075 3 жыл бұрын
@@Eigensteve Thanks for your lecture series. Hope you can respond to my other message when you can.
@amuprakash25
@amuprakash25 3 жыл бұрын
could you please do a lecture on curvelets. Thanks!
@germanyafricansoul8269
@germanyafricansoul8269 3 жыл бұрын
deal steve, love your book, but in your book page 22, formel 1.26 , you may means B=X- avg(X ) ?
@bulutosman
@bulutosman 2 жыл бұрын
Awesome videos. Thank you so much for your effort. But the python and Matlab links on the website direct me to this video again. How can I reach the codes?
@marllonmoraes658
@marllonmoraes658 2 жыл бұрын
Teacher, can you make the notebooks of this chapter available? This topic is very interesting
@prashantsharmastunning
@prashantsharmastunning 3 жыл бұрын
its all coming together..
@Eigensteve
@Eigensteve 3 жыл бұрын
I love it when that happens
@germanyafricansoul8269
@germanyafricansoul8269 3 жыл бұрын
and on page 23. Code 1.10 added the code für PCA coodinate would be helpful, otherwise we love you, greeting from germany :)
@germanvillalobos3728
@germanvillalobos3728 Жыл бұрын
I'm not sure if this question make sense, but if s corresponds to the Fourier transform of x, would that mean that Psi technically corresponds to the inverse of the Fourier basis? If Psi corresponds to the Fourier basis, then applying Psi to a vector would technically correspond to taking its Fourier transform.
@cz5672
@cz5672 Жыл бұрын
Why is s=(Theta+)y called L2 solution? I thought there should be an extra L2 norm (||s||_2) to penalize before it can be called L2 solution. Am I missing something?
@rito_ghosh
@rito_ghosh Жыл бұрын
How exactly does the L1 and the L2 norm make the difference in the values and nature of X? I would really like to know that. Exactly what happens and how- that is my question.
@nischalsehrawat2130
@nischalsehrawat2130 3 жыл бұрын
Hi Steve can you please do a series on time series analysis?
@Eigensteve
@Eigensteve 3 жыл бұрын
Absolutely. I have bits and pieces of this floating around, but maybe something more consolidated would be good.
@nischalsehrawat2130
@nischalsehrawat2130 3 жыл бұрын
@@Eigensteve Thanks. I started with your control series and I made my own Segway (studio.kzfaq.infoLzBVJ7Rq4XY/edit). I can't thank you enough. Looking forward to time series analysis.
@CsatiZoli272
@CsatiZoli272 3 жыл бұрын
According to the histogram, there are many very small, but still not zero solution components for vector s after the L1 minimization. Are those tiny entries rounded to 0 to obtain a truly sparse solution vector (denote it by ss)? If done so, is it always guaranteed that the Theta*ss - y is small? I ask it because it reminds me of the process when a mixed integer linear programming is replaced by a mixed linear programming problem and the corresponding optimum can largely differ.
@parskatt2971
@parskatt2971 3 жыл бұрын
I guess the error is gonna be bounded by something like ||theta||*||s-ss|| (where ||theta|| is some matrix norm, either 1 norm or 2 norm). For fourier stuff with sampling you have a unitary matrix followed by discrete sampling which means that you would have ||theta|| < 1with some handwaving, so hence the error should be decently small I guess.
@systemx6603
@systemx6603 3 жыл бұрын
Most algorithms out there for solving these type of systems employ a shrinkage operator to ensure that those entries do in fact become zero.
@CsatiZoli272
@CsatiZoli272 3 жыл бұрын
@@systemx6603 Thank you. Now that I know what keyword to look for, I can read more about it.
@parskatt2971
@parskatt2971 3 жыл бұрын
I think it would be more instructive if you actually generated y from some sparse vector
@parskatt2971
@parskatt2971 3 жыл бұрын
@@var67 yes i know, thats why i mean y should be generated through some sparse s times theta
@CsatiZoli272
@CsatiZoli272 3 жыл бұрын
How would that be more instructive?
@parskatt2971
@parskatt2971 3 жыл бұрын
@@CsatiZoli272 you could for example actually compare the true vector with the estimated one for both the l2 and l1 case
@parskatt2971
@parskatt2971 3 жыл бұрын
@@CsatiZoli272 Here I made a plot of how the solution actually compares (using n=500, p=200): i.imgur.com/q2aj4IR.png
@CsatiZoli272
@CsatiZoli272 3 жыл бұрын
@@parskatt2971 What is gt? It seems to be a manufactured solution for vector s with the first few entries being non-zero (i.e. 1). Did you use the L2 minimizer as an initial vector?
@sdal4926
@sdal4926 2 жыл бұрын
Very good lectures but I have one critisim. there are many repetition during the class so makes difficult to follow. You have already explained y, theta and x. So you can directly go on.
@fullmetalschizoid
@fullmetalschizoid 2 жыл бұрын
Why didn't you just use Lasso regression? Much faster
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