MATLAB: How create correct function

function

Hi I wrote something like that and I think it is a function but I got some errors when I run it. What is mistake?

 function t = Aineq(k1,q,e,a,b)
m=input('input m=')
n=input('input n=')
q=sparse(m*n,m*n)
e=speye(m*n)
k1=-4*e
a=constraint12b(m,n)
b=constraint12c(m,n)
t=[k1 q e q;q k1 q e;a q e q;q a q e;b q -e q;q b q -e]
end

I point that constraint12b and constraint12c are functions separately and could be ran correctly.

Best Answer

Your function should be something like this

function t = Aineq(m,n)
q=sparse(m*n,m*n)
e=speye(m*n)
k1=-4*e
a=constraint12b(m,n)
b=constraint12c(m,n)
t=[k1 q e q;q k1 q e;a q e q;q a q e;b q -e q;q b q -e]

save this as Aineq.m, then if you want to run your function, you have to use another script or from Matlab windows command

n=10
m=20
t = Aineq(m,n)

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This looks like a very sparse matrix, right? Then I would first figure out how to assign the blocks of Aineq from its components, something like this:

blksz = [3,13]; % or whatever they become
nBlks = 15;
Aineq = zeros(blksz*nBlks);
for i1 = 1:nBlks
  for i2 = 1:nBlks
    % Some logics here for selecting which block to fill Aineq with
    Aineq((1:blksz(1))+blksz*(i1-1),(1:blksz(2))+blksz(2)*(i2-1)) = CurrBlk;
  end
end

Once you've figured that one out, you should look at what components of every block is non-zero and start to build sparse blocks, and then concatenate them instead, that would be much more memmory efficient. Then the last step (or preferably the firts, but I find it easier to move to sparse representations of comlex matrices step-by-step), is to calculate vectors with the row and column-indices and the corresponding matrix element and then simply concatenate those into three arrays i_rows, i_cols, val and then call sparse:

Asparse = sparse(i_rows,i_cols,vals,nRows,nCols);

HTH

Best Answer

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