Adding 2D array to 3D array within loop

I have a 3d array of zeros size (365,721,1440). I'm iterating through a for loop to add from array (721,1440) to the 3d array for each 1:365. Effectively, I'm wanting to do something like this:

totalarray(i,:,:)=totalarray(i,:,:)+newdata(:,:);

But obviously that throws me an error (Array dimensions must match for binary array op). Any idea how to add this new data I'm creating with each iteration to the total array?

[Stephen23]

The robust approach avoiding SQUEEZE is to use PERMUTE, e.g. inside the loop:

totalarray(i,:,:) = totalarray(i,:,:) + permute(newdata(:,:),[3,1,2]);

Answer 1

[Torsten]

totalarray = rand(365,721,1440);
newdata = rand(721,1440);
squeeze(totalarray(1,:,:))

ans = 721×1440

0.9180 0.7403 0.9442 0.6863 0.8394 0.5977 0.4434 0.9624 0.6240 0.7789 0.5832 0.5035 0.7979 0.4041 0.5983 0.3894 0.2274 0.2399 0.4560 0.0206 0.4144 0.6171 0.3203 0.0168 0.8789 0.5111 0.8552 0.4301 0.6461 0.6321 0.3525 0.9185 0.0988 0.5666 0.2365 0.2108 0.9625 0.1204 0.2400 0.8816 0.3561 0.6151 0.7968 0.7438 0.2618 0.6526 0.0194 0.4032 0.9423 0.4526 0.7445 0.3585 0.4404 0.9950 0.8167 0.2546 0.8617 0.3610 0.0185 0.5758 0.9099 0.9810 0.0050 0.4039 0.9070 0.7620 0.4528 0.9870 0.2616 0.4812 0.3090 0.8578 0.7012 0.6637 0.2347 0.4635 0.2407 0.8730 0.2824 0.5364 0.9783 0.8739 0.9082 0.3018 0.4118 0.5963 0.6822 0.5497 0.7222 0.2409 0.3404 0.3833 0.1079 0.3026 0.8795 0.7419 0.3381 0.9935 0.2534 0.3623 0.9849 0.8293 0.7670 0.3845 0.8292 0.2274 0.6246 0.7675 0.0875 0.8846 0.7229 0.9455 0.4574 0.2916 0.3537 0.2259 0.7163 0.4403 0.5925 0.4643 0.6796 0.7045 0.9304 0.4964 0.6210 0.7121 0.4238 0.1424 0.6906 0.6048 0.6481 0.9398 0.4049 0.9680 0.3860 0.8715 0.9419 0.8070 0.9225 0.9702 0.0564 0.5348 0.4018 0.1418 0.5718 0.6908 0.2867 0.7117 0.9550 0.3775 0.1733 0.4875 0.7058 0.4508 0.8729 0.5887 0.2104 0.4657 0.5697 0.8856 0.2466 0.1478 0.1918 0.4356 0.3903 0.4003 0.8102 0.7488 0.2213 0.8581 0.2131 0.1030 0.3792 0.1844 0.2401 0.7674 0.7793 0.0751 0.0511 0.0766 0.5268 0.5218 0.8256 0.8983 0.2225 0.4608 0.2592 0.3078 0.1806 0.0341 0.0125 0.7160 0.3720 0.0708 0.5327 0.7104 0.2295 0.4033 0.0143 0.1474 0.4705 0.9806 0.7691 0.7418 0.9536 0.7874 0.3542 0.1520 0.2379 0.2383 0.2001 0.0328 0.2337 0.3656 0.3641 0.6681 0.8772 0.4709 0.3654 0.2162 0.0318 0.2055 0.4044 0.9056 0.8325 0.3972 0.2610 0.6769 0.2282 0.9662 0.0612 0.8916 0.2086 0.3956 0.9327 0.9214 0.4151 0.4498 0.5307 0.4012 0.0485 0.0869 0.7273 0.9606 0.4810 0.1507 0.4744 0.7508 0.2955 0.3601 0.1234 0.0952 0.2242 0.0694 0.2134 0.0094 0.3020 0.3279 0.1929 0.0123 0.9108 0.1594 0.1994 0.0373 0.2910 0.1065 0.9818 0.2966 0.5297 0.6438 0.6840 0.3363 0.2713 0.3576 0.7629 0.2958 0.5539 0.6363 0.1863 0.6901 0.3004 0.1815 0.4398 0.0904 0.5276 0.3253 0.0399 0.4353 0.2279 0.3832 0.7812 0.5513 0.7459 0.2446 0.2601 0.1010 0.7443 0.7047 0.1154 0.9106

newdata

newdata = 721×1440

0.3055 0.9525 0.1939 0.5656 0.3264 0.4077 0.2867 0.1277 0.5417 0.2422 0.8504 0.9468 0.7681 0.7222 0.2938 0.2369 0.3955 0.9816 0.1759 0.6876 0.7899 0.3958 0.7094 0.3803 0.8130 0.1588 0.5729 0.1190 0.7107 0.0030 0.7729 0.7734 0.5378 0.1872 0.7650 0.7394 0.6198 0.8529 0.5647 0.4154 0.4782 0.8490 0.6765 0.5201 0.1543 0.8161 0.2849 0.8946 0.4749 0.2000 0.0452 0.4117 0.3485 0.5924 0.4287 0.2122 0.9401 0.2599 0.8172 0.8658 0.6798 0.8855 0.3265 0.2858 0.0643 0.3721 0.2426 0.4622 0.0092 0.4493 0.0270 0.8284 0.1620 0.8471 0.5345 0.2865 0.4786 0.2376 0.7596 0.4692 0.0854 0.4451 0.3848 0.2226 0.0683 0.8597 0.6666 0.9165 0.9614 0.1105 0.5993 0.9617 0.5919 0.0541 0.0755 0.3134 0.9879 0.8500 0.7821 0.4782 0.9411 0.2385 0.1511 0.4519 0.4333 0.8353 0.4779 0.8709 0.0190 0.0670 0.6135 0.0584 0.5449 0.1919 0.7425 0.1847 0.2467 0.8357 0.1343 0.6207 0.4026 0.3645 0.8392 0.0831 0.9765 0.8641 0.0740 0.2607 0.7417 0.9087 0.8713 0.7614 0.0320 0.9100 0.6449 0.5718 0.7865 0.9480 0.9700 0.2585 0.2334 0.9652 0.3249 0.8944 0.0340 0.0967 0.4310 0.8865 0.3138 0.6828 0.4058 0.8199 0.3658 0.2186 0.7358 0.8380 0.4910 0.7623 0.6318 0.1847 0.2507 0.2270 0.7121 0.1699 0.0554 0.1013 0.7941 0.2391 0.1909 0.1481 0.8970 0.7278 0.3771 0.1150 0.2383 0.5073 0.8240 0.8893 0.1994 0.6386 0.2944 0.3914 0.3253 0.4870 0.8307 0.2496 0.7897 0.4705 0.9255 0.9174 0.0917 0.9445 0.4681 0.3413 0.5292 0.8798 0.9710 0.8278 0.6057 0.9887 0.2685 0.6637 0.9822 0.5773 0.8273 0.1851 0.6225 0.5118 0.0222 0.5489 0.7444 0.7727 0.0729 0.2738 0.7131 0.0560 0.7964 0.8715 0.8032 0.8399 0.6415 0.7498 0.6395 0.3618 0.9688 0.5533 0.1456 0.1894 0.8611 0.4335 0.1508 0.5761 0.7659 0.0973 0.2885 0.7930 0.3601 0.5473 0.2266 0.0614 0.9997 0.9776 0.1400 0.0641 0.8306 0.5158 0.6687 0.4564 0.2149 0.5413 0.9368 0.5342 0.5678 0.6941 0.1299 0.2821 0.2538 0.5806 0.2616 0.7413 0.1544 0.8241 0.6549 0.8108 0.6849 0.6357 0.1402 0.3796 0.5517 0.7123 0.9054 0.4918 0.4470 0.6017 0.7618 0.5326 0.0907 0.8633 0.7658 0.2938 0.1662 0.6496 0.2920 0.4888 0.4386 0.4805 0.6625 0.9880 0.9101 0.7173 0.6183 0.6784 0.8134 0.0029 0.5616 0.3775 0.9112 0.7606 0.1493 0.3026

for i = 1:365
    totalarray(i,:,:)=squeeze(totalarray(i,:,:))+newdata(:,:);
end
squeeze(totalarray(1,:,:))-newdata

ans = 721×1440

0.9180 0.7403 0.9442 0.6863 0.8394 0.5977 0.4434 0.9624 0.6240 0.7789 0.5832 0.5035 0.7979 0.4041 0.5983 0.3894 0.2274 0.2399 0.4560 0.0206 0.4144 0.6171 0.3203 0.0168 0.8789 0.5111 0.8552 0.4301 0.6461 0.6321 0.3525 0.9185 0.0988 0.5666 0.2365 0.2108 0.9625 0.1204 0.2400 0.8816 0.3561 0.6151 0.7968 0.7438 0.2618 0.6526 0.0194 0.4032 0.9423 0.4526 0.7445 0.3585 0.4404 0.9950 0.8167 0.2546 0.8617 0.3610 0.0185 0.5758 0.9099 0.9810 0.0050 0.4039 0.9070 0.7620 0.4528 0.9870 0.2616 0.4812 0.3090 0.8578 0.7012 0.6637 0.2347 0.4635 0.2407 0.8730 0.2824 0.5364 0.9783 0.8739 0.9082 0.3018 0.4118 0.5963 0.6822 0.5497 0.7222 0.2409 0.3404 0.3833 0.1079 0.3026 0.8795 0.7419 0.3381 0.9935 0.2534 0.3623 0.9849 0.8293 0.7670 0.3845 0.8292 0.2274 0.6246 0.7675 0.0875 0.8846 0.7229 0.9455 0.4574 0.2916 0.3537 0.2259 0.7163 0.4403 0.5925 0.4643 0.6796 0.7045 0.9304 0.4964 0.6210 0.7121 0.4238 0.1424 0.6906 0.6048 0.6481 0.9398 0.4049 0.9680 0.3860 0.8715 0.9419 0.8070 0.9225 0.9702 0.0564 0.5348 0.4018 0.1418 0.5718 0.6908 0.2867 0.7117 0.9550 0.3775 0.1733 0.4875 0.7058 0.4508 0.8729 0.5887 0.2104 0.4657 0.5697 0.8856 0.2466 0.1478 0.1918 0.4356 0.3903 0.4003 0.8102 0.7488 0.2213 0.8581 0.2131 0.1030 0.3792 0.1844 0.2401 0.7674 0.7793 0.0751 0.0511 0.0766 0.5268 0.5218 0.8256 0.8983 0.2225 0.4608 0.2592 0.3078 0.1806 0.0341 0.0125 0.7160 0.3720 0.0708 0.5327 0.7104 0.2295 0.4033 0.0143 0.1474 0.4705 0.9806 0.7691 0.7418 0.9536 0.7874 0.3542 0.1520 0.2379 0.2383 0.2001 0.0328 0.2337 0.3656 0.3641 0.6681 0.8772 0.4709 0.3654 0.2162 0.0318 0.2055 0.4044 0.9056 0.8325 0.3972 0.2610 0.6769 0.2282 0.9662 0.0612 0.8916 0.2086 0.3956 0.9327 0.9214 0.4151 0.4498 0.5307 0.4012 0.0485 0.0869 0.7273 0.9606 0.4810 0.1507 0.4744 0.7508 0.2955 0.3601 0.1234 0.0952 0.2242 0.0694 0.2134 0.0094 0.3020 0.3279 0.1929 0.0123 0.9108 0.1594 0.1994 0.0373 0.2910 0.1065 0.9818 0.2966 0.5297 0.6438 0.6840 0.3363 0.2713 0.3576 0.7629 0.2958 0.5539 0.6363 0.1863 0.6901 0.3004 0.1815 0.4398 0.0904 0.5276 0.3253 0.0399 0.4353 0.2279 0.3832 0.7812 0.5513 0.7459 0.2446 0.2601 0.1010 0.7443 0.7047 0.1154 0.9106

[Bruno Luong]

I'm confused as a MATLAB beginner (!)

I though such assigment

totalarray(i,:,:)=squeeze(totalarray(i,:,:))+newdata(:,:);

would throw an error

"Unable to perform assignment because the size of the left side is 1-by-721-by-1440 and the size of the right side is 721-by-1440."

but obviously it's not.

Can someone points me to the official document that explain such assigment is allowed and how?

[Torsten]

Assigning an 1d row vector to the ith row of a matrix is the same thing:

v = rand(1,5);
M = zeros(3,5);
M(3,:) = v

M = 3×5

0 0 0 0 0 0 0 0 0 0 0.8197 0.2924 0.0199 0.8188 0.6605

[Bruno Luong]

Can you modify my (wrong) allowedassgn below so that it reflects correctly when the assignment

lhs = rhs

is allowed?

allowedassgn = @(lhs,rhs) isequal(size(lhs), size(rhs)) || ...
              (isvector(lhs) && isvector(rhs) && length(lhs)==length(rhs)) || ...
              (isempty(rhs) && isempty(lhs));

v = rand(1,5);
M = zeros(3,5);
allowedassgn(M(3,:), v)

ans = logical
   1

M(3,:) = v; % so this is allowed

v = rand(5,1);
M = zeros(3,5);
allowedassgn(M(3,:), v) % idem

ans = logical
   1

M(3,:) = v

M = 3×5

0 0 0 0 0 0 0 0 0 0 0.1687 0.1125 0.1724 0.9949 0.6670

v = rand(4,5);
M = zeros(3,4,5);
allowedassgn(M(3,:,:), v)

ans = logical
   0

M(3,:,:) = v % but this works !!!

M = 
M(:,:,1) =

         0         0         0         0
         0         0         0         0
    0.6594    0.8731    0.3168    0.0578


M(:,:,2) =

         0         0         0         0
         0         0         0         0
    0.2092    0.0008    0.4694    0.9609


M(:,:,3) =

         0         0         0         0
         0         0         0         0
    0.1171    0.4693    0.2653    0.1701


M(:,:,4) =

         0         0         0         0
         0         0         0         0
    0.3111    0.4261    0.2979    0.8661


M(:,:,5) =

         0         0         0         0
         0         0         0         0
    0.4661    0.3910    0.2764    0.9486

[Torsten]

Maybe

allowedassgn = @(lhs,rhs) isequal(size(squeeze(lhs)), size(rhs)) || ...
    (isvector(lhs) && isvector(rhs) && length(lhs)==length(rhs)) || ...
    (isempty(rhs) && isempty(lhs));

?

[Bruno Luong]

But

allowedassgn = @(lhs,rhs) isequal(size(squeeze(lhs)), size(rhs)) || ...
    (isvector(lhs) && isvector(rhs) && length(lhs)==length(rhs)) || ...
    (isempty(rhs) && isempty(lhs));

fails to detect

M = zeros(3,4,5);
v=rand(1,4,5);
allowedassgn(M(1,:,:),v)

ans = logical
   0

M(1,:,:)=v; % But this works

[Bruno Luong]

I think I'll ask in a separete question to get more visible to others