set some values to zero in a matrix or vector

Hi everyone,

I am doing the svd in Simulink, I got the eigenvalue, now I want to set some eigenvalues smaller than a given value to zero. for example, if the eigenvalue small than 2, i set it to zero and keep the those eigen values large than 2 unchanged, incuding the place in the matix and the value.

PS: my matlab is 2009b, there are no Find block. so I can not use that block to find the zero value also.

Thank you very much!

Answer 1

[Fangjun Jiang]

How do you do it in Simulink? It sounds like a Matlab data processing problem, e.g.

a=4*rand(3,3)
a(a<2)=0

If you do it in Simulink, what I can think of is that you demux your matrix to individual value, and then use a switch block to compare these individual value, if it is less than 2 then output zero, otherwise, pass it through. At the end, mux them together.

[Hongmei Hu]

Hi Fangjun,

Thank you for the answer, it is a solution, but if the number of eigenvalues is more than 10 or much more than 10, this method will be too complex, is it possible to find the index of the eigenvalue, and then set those smaller than 2 to zero, and keep the others unchanged?

Thank you.

[Oleg Komarov]

That's what Fangjun's solution does. Did you try his snippet?

[Fangjun Jiang]

@Oleg, I think she is asking if there is an easier way to do it in Simulink. The approach I suggested above in Simulink is a brutal force approach.

@Hongmei Hu, Is there a particular reason that you have to do it in Simulink? To me, SVD is best dealt with using Matlab.