MATLAB: Index exceeds matrix dimension

indexingmatrix dimension

v_m generates a 2 by 5 matrix. inside the for loop at the point after 'else'(basically when i==2), then i am getting an error saying : index exceeds matrix dimensions. why does it happen? when i manually write this: a=alpha0(2); i get the 2nd element of that matrix, but it does not seem to work when it is inside the loop.
alpha0=v_m(:,1);
for i=1:2
  if i==1
     alpha0=alpha0(i);
  else 
     alpha0=alpha0(i);
  end
end

Best Answer

In the first iteration, i=1, you evaluate
alpha0 = alpha0(i);
This replaces the vector alpha0 by the scalar alpha0(1). Afterwards, alph0(2) does not exist anymore.
I cannot imagine the purpose of the shown code. Therefore it is hard to suggest a solution. Maybe
alpha0 = v_m(:,1);
for i=1:2
  currentAlpha0 = alpha0(i);
  ... and here the computations
end
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