Multiplying a changing amount matrices.

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Youri
Youri 2013-11-18
评论： Youri 2013-11-25
the problem I am struggeling with is to multiply a known, but depending on the application, changing amount of matrices (2x2). I would like to write a code that does this without me having to manually enter the matrix names. It would work like horzcat() but for a different amount of matrices every time i use the program. Currently this is what it should do:
for i_freq=1:length(freq) omega=2*pi*freq(i_freq); k=omega/c_0;
%define muffler elements
T1=straight_duct(k,L1);
T2=expansion_duct(E);
T3=straight_duct(k,L2);
T4=contraction_duct(E);
T5=straight_duct(k,L3);
%Transfer transmission matrix
TT=T5*T4*T3*T2*T1;
%extract elements from matrix
A=TT(1,1)
B=TT(1,2)
C=TT(2,1)
D=TT(2,2)
F=A-C/D;
T=[A B; C D];
%Transmission loss
TL(i_freq)=20*log10(abs(F));
end
I'm pretty new to matlab so a shove in the right direction would be nice. I've been looking at plenty of topics but none have actually resolved this problem for me (dynamic matrices, dynamic variables, recognizable variables). The order of the multiplication matters.
hope some one can show me the light with which i can continue working!
cheers.

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采纳的回答

Youri
Youri 2013-11-22
Thank you very much for your reply, the 3D matrix was something that is new to me and i am currently using. It's an awesome way of saving our arrays. The problem I'm still having is the product, I will have to think of a different way of resolving this issue.
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Simon
Simon 2013-11-25
I'm sorry, I misunderstood the problem. You want to multiply the matrices, whereas I thought (and this is what "prod" does) you want to multiply the entries of the matrix.
Youri
Youri 2013-11-25
ah, sorry for the misleading info. Still new to all of this so the correct way of paraphrasing my questions is not a skill i have yet :) you pointed me in the right direction which was what i ultimately needed

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更多回答（1 个）

Simon
Simon 2013-11-18
Hi!
I'm not sure if I understood correctly. You can concat N matrices into a 3d matrix with dimensions (2x2xN). Basically, you stack them together. Then you may use "prod" to take the product along the third dimension.
%define muffler elements
T(1:2, 1:2, 1)=straight_duct(k,L1);
T(1:2, 1:2, 2)=expansion_duct(E);
T(1:2, 1:2, 3)=straight_duct(k,L2);
T(1:2, 1:2, 4)=contraction_duct(E);
T(1:2, 1:2, 5)=straight_duct(k,L3);
%Transfer transmission matrix
TT=prod(T, 3);
Is this what you're looking for?

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