MATLAB: Preallocate an matrix in 2 for loops

MATLABpreallocate

How would I preallocate This matrix?

for j=1:numel(A)
    for i=1:numel(A)
        B(j,i)="Calculation here"
    end
end

N=numel(A);
B=zeros(N,N); %This is how
for j=1:N
    for i=1:N
        B(j,i)="Calculation here"
    end
end

for j = [1:i-1, i+1:n]
  ...
end

is the same as:

for j = 1:n
  if j ~= i
     ...
  end
end

It runs a loop over all numbers from 1 to n, but excludes i . The loop index is the concatenation of the vectors 1:i-1 and i+1:n .

You can simply try it:

n = 10;
i = 7;
for j = [1:i-1, i+1:n]
  disp(j)
end

Jacobian=D2Mat(2:end-1,:)+(2./XCheb(2:end-1)).*D1Mat(2:end-1,:)+((xi^2)*n*Y(2:end-1).^(n-1)).*D0Mat(2:end-1,:);