multiplication of matrix with long data

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michael 2022-7-14

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https://ww2.mathworks.cn/matlabcentral/answers/1759580-multiplication-of-matrix-with-long-data

评论： Steven Lord 2023-2-28

Hi,

I have a long data (200K+ samples) from which a location vector L (3x1) and a matrix T (euler matrix 3x3) is generated and multiplied l = TL.

On the results of l (3x1) there are operations of sin and atan (to get the required results).

So far, I'm doing a for loop, which is not a Matlab way.

I'd like to speedup the performance of the code.

How can I do it?

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Bruno Luong 2022-7-14

"So far, I'm doing a for loop, which is not a Matlab way. "

Anything allowed by MATLAB IS MATLAB way.

Steven Lord 2023-2-28

Is there a specific reason you're still using release R14SP2 which is pretty close to twenty years old at this point?

There have been a lot of improvements in MATLAB in the past twenty years, which likely would improve performance of your code.

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采纳的回答

Bruno Luong 2022-7-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1759580-multiplication-of-matrix-with-long-data#answer_1007140

编辑：Bruno Luong 2022-7-14

在 MATLAB Online 中打开

% Test data
N = 4;
Phi     = 2*pi*rand(1,N);
Theta   = 2*pi*rand(1,N);
Psi     = 2*pi*rand(1,N);
X       = rand(1,N);
Y       = rand(1,N);
Z       = rand(1,N);
Phi     = reshape(Phi,      1, 1, []);
Theta   = reshape(Theta,    1, 1, []);
Psi     = reshape(Psi,      1, 1, []);
X       = reshape(X,        1, 1, []);
Y       = reshape(Y,        1, 1, []);
Z       = reshape(Z,        1, 1, []);
sB = sin(Phi);   cB = cos(Phi);
sD = sin(Theta); cD = cos(Theta);
sE = sin(Psi);   cE = cos(Psi);
T = [ cD.*cE, -cB.*sE+cE.*sB.*sD,  sB.*sE+cB.*sD.*cE;
      cD.*sE,  cB.*cE+sB.*sD.*sE, -cE.*sB+cB.*sD.*sE;
         -sD,             sB.*cD,             cB.*cD ];
XYZ = [X; Y; Z];
xyz = pagemtimes(T, XYZ)
xyz = 
xyz(:,:,1) =

    0.3128
    0.5127
   -0.3960


xyz(:,:,2) =

   -0.7072
   -0.7636
    0.1150


xyz(:,:,3) =

   -0.1876
    0.0750
    1.0194


xyz(:,:,4) =

    1.2058
   -0.6237
    0.2521
% For older MATLAB
%XYZ = [X, Y, Z];
%xyz = sum(T.*XYZ,2)

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michael 2023-2-28

Please note that I'm using old version Matlab R14

Bruno Luong 2023-2-28

编辑：Bruno Luong 2023-2-28

在 MATLAB Online 中打开

The inverse of T is its transpose T.', you need to form the inverse, noted here by iT

iT = [ cD.*cE,             cD.*sE,            -sD;
      -cB.*sE+cE.*sB.*sD,  cB.*cE+sB.*sD.*sE, sB.*cD;
       sB.*sE+cB.*sD.*cE,  cE.*sB+cB.*sD.*sE, cB.*cD ];
% For older MATLAB
XYZ = [X, Y, Z];
xyz = sum(iT.*XYZ,2)