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

Dyl
7 Sep 2022
3 Answers
Answer Accepted
Updated 8 Sep 2022
5 Views (30 days)

0 votes

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.

Sign in to answer this question.

 Accepted Answer

Stephen23
Stephen23 on 7 Sep 2022
Ran in:

0 votes

Ran in:
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}

6 Comments
Show 4 older comments Hide 4 older comments

Dyl
Dyl on 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 on 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 on 7 Sep 2022
Ran in:
Ran in:
"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 on 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.

Sign in to comment.

More Answers (2)

KSSV
KSSV on 7 Sep 2022

0 votes

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 on 7 Sep 2022
Ran in:

0 votes

Ran in:
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

2 Comments
Show None Hide None

Stephen23
Stephen23 on 7 Sep 2022
Edited: Stephen23 on 7 Sep 2022
Ran in:
Ran in:
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 on 7 Sep 2022
Thanks @Stephen23. But he does not mention that the order must be te same as in the original matrix!

Sign in to comment.

Categories

Find more on Matrix Indexing in Help Center and File Exchange

Tags

Asked:

Dyl
Dyl
on 7 Sep 2022

Commented:

Stephen23
Stephen23
on 8 Sep 2022

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!