How to make a m*2 matrix into n number of 2x2 matrices

Dyl
7 Sep 2022
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Mise à jour 8 Sep 2022
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Hey,
I have, A = 208x2 matrix. I wish to to spit this matrix into 104 2x2 matrices. I have tried using num2cell and mat2cell but have had no luck. Any help would be appreicated.
Thanks.

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Stephen23
Stephen23 le 7 Sep 2022
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A = rand(208,2);
C = mat2cell(A,2*ones(104,1),2)
C = 104×1 cell array
{2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double} {2×2 double}

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Dyl
Dyl le 7 Sep 2022
Thank you this works. I also have another question.
I wanted to create these 2x2 matrices so I could complete x=A\B to find the unknowns, the two forces acting upon a point. The 2x2 matrices is the matrices requried for each possible coordinate of the point subjected to two forces.
I have B = [0;62.4051] and when I try x=A\B it states there is an error 'Arguments must be numeric, char, or logical,' Do you know how I overcome this error?
Dyl
Dyl le 7 Sep 2022
I will elaborate on this to ensure clarity.
There are two unknown forces F1 and F2. They are acting upon point J. Point J is in a carteisan grid and therefore, has x number of possible locations. I have calculated the matrices for each location of point J and x=A\B is to calculate the two unknown forces (F1 and F2) for each possible J point. That is why there are 104 2x2 matrices because I wish to solve the system of equations for each point. However, Matlab will not allow for the calculations because of the error stated above.
Stephen23
Stephen23 le 7 Sep 2022
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"I wanted to create these 2x2 matrices so I could complete x=A\B to find the unknowns..."
A = rand(208,2);
B = [0;62.4051];
1) loop over the cells, or use CELLFUN:
C = mat2cell(A,2*ones(104,1),2);
D = cellfun(@(a)a\B,C,'uni',0)
D = 104×1 cell array
{2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double} {2×1 double}
D{1:5}
ans = 2×1
254.7375 -448.7160
ans = 2×1
-201.0346 269.0615
ans = 2×1
-15.4333 244.1028
ans = 2×1
-37.7452 115.8506
ans = 2×1
242.8873 -256.4729
2) avoid the cell array entirely: call PERMUTE&RESHAPE the data, and then call PAGEMLDIVIDE: https://www.mathworks.com/help/matlab/ref/pagemldivide.html
N = permute(reshape(A.',2,2,[]),[2,1,3]);
Z = pagemldivide(N,B)
Z =
Z(:,:,1) = 254.7375 -448.7160 Z(:,:,2) = -201.0346 269.0615 Z(:,:,3) = -15.4333 244.1028 Z(:,:,4) = -37.7452 115.8506 Z(:,:,5) = 242.8873 -256.4729 Z(:,:,6) = 399.4539 -465.6991 Z(:,:,7) = 103.4845 -57.6442 Z(:,:,8) = 201.3918 -300.9553 Z(:,:,9) = 71.7649 -11.7430 Z(:,:,10) = -140.2163 121.2142 Z(:,:,11) = -249.7239 339.4336 Z(:,:,12) = -74.7253 92.1409 Z(:,:,13) = -71.2602 76.4186 Z(:,:,14) = -51.0881 208.3873 Z(:,:,15) = 137.9599 -54.1809 Z(:,:,16) = 87.1851 -38.8293 Z(:,:,17) = 213.9198 -256.6160 Z(:,:,18) = -184.3306 387.9273 Z(:,:,19) = -83.0493 184.3273 Z(:,:,20) = 190.0474 -180.4605 Z(:,:,21) = 93.1972 -162.9662 Z(:,:,22) = 1.0e+03 * -1.6875 1.1888 Z(:,:,23) = -157.0278 165.5029 Z(:,:,24) = 1.0e+03 * -1.1328 0.6363 Z(:,:,25) = 1.0e+03 * 2.7605 -1.5682 Z(:,:,26) = -141.5120 226.2982 Z(:,:,27) = 457.9589 -677.7478 Z(:,:,28) = -43.5975 101.2070 Z(:,:,29) = 294.5180 -179.8068 Z(:,:,30) = 455.4697 -141.1948 Z(:,:,31) = 174.2676 -91.3634 Z(:,:,32) = 291.5284 -317.2197 Z(:,:,33) = 1.0e+03 * 2.6183 -1.0546 Z(:,:,34) = 1.0e+03 * -3.6468 3.4186 Z(:,:,35) = -26.2973 82.2843 Z(:,:,36) = 92.9864 -399.6707 Z(:,:,37) = -313.3782 334.0579 Z(:,:,38) = 1.0e+03 * 0.5017 -3.2983 Z(:,:,39) = -25.1379 78.3355 Z(:,:,40) = -60.8443 158.5588 Z(:,:,41) = -126.9928 245.6587 Z(:,:,42) = 138.7083 -77.8317 Z(:,:,43) = -73.1815 99.4966 Z(:,:,44) = -29.2873 152.2512 Z(:,:,45) = 117.8240 -1.3511 Z(:,:,46) = 377.8151 -423.7863 Z(:,:,47) = -972.7903 398.6766 Z(:,:,48) = -718.3835 784.9308 Z(:,:,49) = -347.1907 359.5996 Z(:,:,50) = 1.0e+03 * 3.4663 -1.6957 Z(:,:,51) = -679.9005 433.6712 Z(:,:,52) = 85.1131 -13.1754 Z(:,:,53) = 74.8836 -2.8372 Z(:,:,54) = 139.1516 -24.7928 Z(:,:,55) = -20.8858 235.3895 Z(:,:,56) = -37.8064 109.0375 Z(:,:,57) = -80.3218 92.2070 Z(:,:,58) = 1.0e+03 * 1.1045 -1.3925 Z(:,:,59) = 178.5230 -47.1629 Z(:,:,60) = 407.5570 -464.2490 Z(:,:,61) = 1.0e+03 * 1.7465 -0.3442 Z(:,:,62) = -16.3257 455.7497 Z(:,:,63) = -23.1154 132.7811 Z(:,:,64) = 1.0e+04 * -1.6290 0.9430 Z(:,:,65) = -27.6003 81.3097 Z(:,:,66) = 1.0e+03 * -1.4705 1.7093 Z(:,:,67) = 1.0e+03 * -1.9158 1.4897 Z(:,:,68) = 690.1267 -526.2135 Z(:,:,69) = 86.3370 -27.2462 Z(:,:,70) = -50.0804 285.7423 Z(:,:,71) = -25.8221 79.6419 Z(:,:,72) = 81.4405 -87.0205 Z(:,:,73) = -12.2335 74.8112 Z(:,:,74) = 1.0e+03 * -0.5944 1.2712 Z(:,:,75) = 112.3409 -86.8035 Z(:,:,76) = 98.5285 -13.9627 Z(:,:,77) = -149.9494 175.6624 Z(:,:,78) = 167.1853 -77.1778 Z(:,:,79) = 174.2291 -206.0751 Z(:,:,80) = 113.1018 -19.5503 Z(:,:,81) = 215.3669 -47.3075 Z(:,:,82) = -162.0178 200.6032 Z(:,:,83) = 885.2354 -250.7677 Z(:,:,84) = 256.4040 -164.9046 Z(:,:,85) = 1.0e+03 * -0.0817 1.3533 Z(:,:,86) = -23.8031 74.5642 Z(:,:,87) = -124.8749 114.4583 Z(:,:,88) = -56.6865 151.5106 Z(:,:,89) = -20.6243 84.8720 Z(:,:,90) = 81.2266 -30.3164 Z(:,:,91) = 82.7109 -16.0798 Z(:,:,92) = 255.3523 -206.2097 Z(:,:,93) = -423.2773 196.9388 Z(:,:,94) = 1.0e+03 * -0.4201 1.9390 Z(:,:,95) = 321.7179 -89.7420 Z(:,:,96) = -306.0857 229.0526 Z(:,:,97) = -31.1052 97.7231 Z(:,:,98) = 128.2371 -167.8192 Z(:,:,99) = 107.3783 -63.8622 Z(:,:,100) = 1.0e+03 * -1.1572 0.8569 Z(:,:,101) = 262.9194 -369.1406 Z(:,:,102) = -59.1690 144.2688 Z(:,:,103) = 226.9019 -171.2881 Z(:,:,104) = 73.9992 -38.2548
Dyl
Dyl le 7 Sep 2022
Thank you
Dyl
Dyl le 8 Sep 2022
Hey I have another question I reshaped the 2x1x104 matrix into a 13x8 matrix where I only took one value for each val(:,:,1) , valu(:,:,2) etc..
13x8 = [-28,-64 ... ;-33,-74...]
I wanted the values to insert into the 13x8 matric column wise so 1-8 for row 1 then 1-8 for row 2 so on, but they inserted row wise. How can I make the matrix I am after? Thanks in advance.
Stephen23
Stephen23 le 8 Sep 2022
M = reshape(M,8,13).'

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Plus de réponses (2)

KSSV
KSSV le 7 Sep 2022

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A = rand(208,2) ;
[r,c] = size(A);
nlay = 104 ;
out = permute(reshape(A',[c,r/nlay,nlay]),[2,1,3]);
Abderrahim. B
Abderrahim. B le 7 Sep 2022
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Split A
A = randi(10, 208, 2) ; % a mtarix of size 208x2
size(A)
ans = 1×2
208 2
B = reshape(A, 2, 2, []) ;
Access 2x2 matrices
B1 = B(:,:,1)
B1 = 2×2
5 7 9 6
B2 = B(:,:,2)
B2 = 2×2
8 8 4 1
Hope this helps

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Stephen23
Stephen23 le 7 Sep 2022
Modifié(e) : Stephen23 le 7 Sep 2022
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Note that this method does not keep the 2x2 matrices of the original matrix:
A = randi(10, 208, 2)
A = 208×2
3 1 9 7 9 3 4 9 8 7 5 5 4 4 9 1 8 10 10 8
B = reshape(A, 2,2,[]) % not the same matrices
B =
B(:,:,1) = 3 9 9 4 B(:,:,2) = 8 4 5 9 B(:,:,3) = 8 5 10 4 B(:,:,4) = 2 1 10 10 B(:,:,5) = 2 5 7 9 B(:,:,6) = 4 7 4 9 B(:,:,7) = 6 9 4 6 B(:,:,8) = 10 9 2 3 B(:,:,9) = 10 4 6 4 B(:,:,10) = 8 5 2 5 B(:,:,11) = 4 2 6 4 B(:,:,12) = 5 1 6 8 B(:,:,13) = 7 4 4 6 B(:,:,14) = 3 7 6 6 B(:,:,15) = 4 4 7 9 B(:,:,16) = 9 6 2 10 B(:,:,17) = 8 9 7 6 B(:,:,18) = 3 3 2 4 B(:,:,19) = 6 1 6 3 B(:,:,20) = 4 3 10 10 B(:,:,21) = 5 9 6 5 B(:,:,22) = 2 2 8 10 B(:,:,23) = 4 8 3 7 B(:,:,24) = 9 7 2 3 B(:,:,25) = 8 10 6 9 B(:,:,26) = 6 7 8 4 B(:,:,27) = 7 10 10 1 B(:,:,28) = 3 9 7 4 B(:,:,29) = 4 3 9 10 B(:,:,30) = 4 5 3 2 B(:,:,31) = 2 5 9 5 B(:,:,32) = 2 9 9 4 B(:,:,33) = 2 1 6 9 B(:,:,34) = 8 1 3 4 B(:,:,35) = 2 4 4 3 B(:,:,36) = 7 1 5 4 B(:,:,37) = 10 7 1 10 B(:,:,38) = 8 1 1 10 B(:,:,39) = 10 4 1 8 B(:,:,40) = 2 7 9 7 B(:,:,41) = 3 10 2 7 B(:,:,42) = 8 5 9 5 B(:,:,43) = 3 10 10 1 B(:,:,44) = 7 9 2 3 B(:,:,45) = 2 10 9 10 B(:,:,46) = 8 1 9 6 B(:,:,47) = 5 8 7 9 B(:,:,48) = 2 2 3 2 B(:,:,49) = 3 2 3 5 B(:,:,50) = 4 2 9 3 B(:,:,51) = 7 10 10 3 B(:,:,52) = 9 5 3 3 B(:,:,53) = 1 3 7 9 B(:,:,54) = 7 4 5 1 B(:,:,55) = 10 2 8 10 B(:,:,56) = 7 8 8 4 B(:,:,57) = 3 3 6 1 B(:,:,58) = 9 2 5 6 B(:,:,59) = 10 9 6 3 B(:,:,60) = 1 9 5 4 B(:,:,61) = 5 9 4 3 B(:,:,62) = 7 9 8 5 B(:,:,63) = 3 7 3 10 B(:,:,64) = 8 10 10 8 B(:,:,65) = 6 10 9 4 B(:,:,66) = 8 2 7 3 B(:,:,67) = 3 6 5 3 B(:,:,68) = 7 5 5 6 B(:,:,69) = 3 6 6 10 B(:,:,70) = 4 4 6 1 B(:,:,71) = 2 7 6 8 B(:,:,72) = 1 6 1 5 B(:,:,73) = 7 1 10 1 B(:,:,74) = 1 3 4 6 B(:,:,75) = 1 4 5 9 B(:,:,76) = 10 10 9 1 B(:,:,77) = 10 2 4 4 B(:,:,78) = 4 8 8 3 B(:,:,79) = 10 1 10 8 B(:,:,80) = 6 5 7 9 B(:,:,81) = 10 9 8 5 B(:,:,82) = 5 5 5 8 B(:,:,83) = 1 8 5 1 B(:,:,84) = 10 4 4 8 B(:,:,85) = 8 7 6 4 B(:,:,86) = 4 10 4 2 B(:,:,87) = 9 6 3 2 B(:,:,88) = 9 7 9 7 B(:,:,89) = 10 8 10 7 B(:,:,90) = 1 3 9 4 B(:,:,91) = 7 4 1 8 B(:,:,92) = 10 9 5 9 B(:,:,93) = 2 4 6 8 B(:,:,94) = 6 3 7 10 B(:,:,95) = 10 9 10 2 B(:,:,96) = 10 5 3 2 B(:,:,97) = 10 4 9 4 B(:,:,98) = 10 5 9 8 B(:,:,99) = 5 7 6 7 B(:,:,100) = 7 10 1 9 B(:,:,101) = 1 2 7 9 B(:,:,102) = 8 3 5 6 B(:,:,103) = 10 10 4 8 B(:,:,104) = 6 10 3 4
To keep the original matrices requires taing into account the order of elements stored in memory:
B = permute(reshape(A.',2,2,[]),[2,1,3])
B =
B(:,:,1) = 3 1 9 7 B(:,:,2) = 9 3 4 9 B(:,:,3) = 8 7 5 5 B(:,:,4) = 4 4 9 1 B(:,:,5) = 8 10 10 8 B(:,:,6) = 5 2 4 10 B(:,:,7) = 2 7 10 8 B(:,:,8) = 1 8 10 4 B(:,:,9) = 2 3 7 6 B(:,:,10) = 5 3 9 1 B(:,:,11) = 4 9 4 5 B(:,:,12) = 7 2 9 6 B(:,:,13) = 6 10 4 6 B(:,:,14) = 9 9 6 3 B(:,:,15) = 10 1 2 5 B(:,:,16) = 9 9 3 4 B(:,:,17) = 10 5 6 4 B(:,:,18) = 4 9 4 3 B(:,:,19) = 8 7 2 8 B(:,:,20) = 5 9 5 5 B(:,:,21) = 4 3 6 3 B(:,:,22) = 2 7 4 10 B(:,:,23) = 5 8 6 10 B(:,:,24) = 1 10 8 8 B(:,:,25) = 7 6 4 9 B(:,:,26) = 4 10 6 4 B(:,:,27) = 3 8 6 7 B(:,:,28) = 7 2 6 3 B(:,:,29) = 4 3 7 5 B(:,:,30) = 4 6 9 3 B(:,:,31) = 9 7 2 5 B(:,:,32) = 6 5 10 6 B(:,:,33) = 8 3 7 6 B(:,:,34) = 9 6 6 10 B(:,:,35) = 3 4 2 6 B(:,:,36) = 3 4 4 1 B(:,:,37) = 6 2 6 6 B(:,:,38) = 1 7 3 8 B(:,:,39) = 4 1 10 1 B(:,:,40) = 3 6 10 5 B(:,:,41) = 5 7 6 10 B(:,:,42) = 9 1 5 1 B(:,:,43) = 2 1 8 4 B(:,:,44) = 2 3 10 6 B(:,:,45) = 4 1 3 5 B(:,:,46) = 8 4 7 9 B(:,:,47) = 9 10 2 9 B(:,:,48) = 7 10 3 1 B(:,:,49) = 8 10 6 4 B(:,:,50) = 10 2 9 4 B(:,:,51) = 6 4 8 8 B(:,:,52) = 7 8 4 3 B(:,:,53) = 7 10 10 10 B(:,:,54) = 10 1 1 8 B(:,:,55) = 3 6 7 7 B(:,:,56) = 9 5 4 9 B(:,:,57) = 4 10 9 8 B(:,:,58) = 3 9 10 5 B(:,:,59) = 4 5 3 5 B(:,:,60) = 5 5 2 8 B(:,:,61) = 2 1 9 5 B(:,:,62) = 5 8 5 1 B(:,:,63) = 2 10 9 4 B(:,:,64) = 9 4 4 8 B(:,:,65) = 2 8 6 6 B(:,:,66) = 1 7 9 4 B(:,:,67) = 8 4 3 4 B(:,:,68) = 1 10 4 2 B(:,:,69) = 2 9 4 3 B(:,:,70) = 4 6 3 2 B(:,:,71) = 7 9 5 9 B(:,:,72) = 1 7 4 7 B(:,:,73) = 10 10 1 10 B(:,:,74) = 7 8 10 7 B(:,:,75) = 8 1 1 9 B(:,:,76) = 1 3 10 4 B(:,:,77) = 10 7 1 1 B(:,:,78) = 4 4 8 8 B(:,:,79) = 2 10 9 5 B(:,:,80) = 7 9 7 9 B(:,:,81) = 3 2 2 6 B(:,:,82) = 10 4 7 8 B(:,:,83) = 8 6 9 7 B(:,:,84) = 5 3 5 10 B(:,:,85) = 3 10 10 10 B(:,:,86) = 10 9 1 2 B(:,:,87) = 7 10 2 3 B(:,:,88) = 9 5 3 2 B(:,:,89) = 2 10 9 9 B(:,:,90) = 10 4 10 4 B(:,:,91) = 8 10 9 9 B(:,:,92) = 1 5 6 8 B(:,:,93) = 5 5 7 6 B(:,:,94) = 8 7 9 7 B(:,:,95) = 2 7 3 1 B(:,:,96) = 2 10 2 9 B(:,:,97) = 3 1 3 7 B(:,:,98) = 2 2 5 9 B(:,:,99) = 4 8 9 5 B(:,:,100) = 2 3 3 6 B(:,:,101) = 7 10 10 4 B(:,:,102) = 10 10 3 8 B(:,:,103) = 9 6 3 3 B(:,:,104) = 5 10 3 4
Abderrahim. B
Abderrahim. B le 7 Sep 2022
Thanks @Stephen23. But he does not mention that the order must be te same as in the original matrix!

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