Unable to perform assignment because the size of the left side is 7-by-1 and the size of the right side is 7-by-7

Hi, I would like to pass some extra arguments to my ODE as follows:

[T,H] =  ode23t(@(t,h) MYODE(t,h,G,N,e,n,z,initialnode,w,Qcell,lambda), tspan, h0, opts);
[~,Qcell] = cellfun(@(t,h) MYODE(t,h,G,N,e,n,z,initialnode,w,Qcell,lambda), num2cell(T), num2cell(H,2), 'uni',0);

but I get this error:

Unable to perform assignment because the size of the left side is 7-by-1 and the size of the right side is 7-by-7.

Any idea on how to fix it?

Answer 1

[Walter Roberson]

The boundary conditions, h, will always be passed to the function as a column vector even if you initialize as a row vector. Your extra arguments have at least one row vector that you are combining elementwise with h thinking that h is a row vector. But because it is a column vector you are getting implicit expansion, as if you had used bsxfun.

Review your code and ensure that you have the right orientation for all your inputs taking into consideration that h will be received as a column vector.

[Sim]

Thanks a lot Walter!!

I checked the code and I got the line which caused the error (it was inside my ODE function)

% The last column of A was updated with h at each ODE iteration
B(:,3) = A(:,3) + h

Here an example about A, B and h

% Example of one iteration of ODE
A =

     0   100    17
   250   100    15
   500   100    12
   750     0     9
   750   200     9
   900     0    18
   900   200    18
   
h =

    0.0080701
    0.0019583
      0.11659
       3.1164
       3.1164
        0.001
        0.001

B =

            0          100       17.008
          250          100       15.002
          500          100       12.117
          750            0       12.116
          750          200       12.116
          900            0       18.001
          900          200       18.001      

I do not know why (?), but at the last iteration h was a row and not a column as usually defined and as correctly outputed during all the previous ODE iterations.

Neverthenless, I worked around it in this way

if isrow(h); h = h'; end

[Walter Roberson]

h(:) would work either way