MATLAB: How to add two vectors of same length or different length using for-loops

for loop

for example: x=[9 9 9 9];y=[9 9 9 9] The result should be as z=[1 9 9 9 8]. How can I write a code using for-loops or any other means. Greatly appreciate help

Best Answer

Using the string conversion is efficient as long as the input does not have more than 16 digits. For longer vectors the limited precision of double will crop the least significant digits. For an arbitrary number of digits:
function c = DigitsAdd(a, b)
% Author: Jan Simon, License: Creative Commons Attribution Share Alike 3.0
isrow = size(a, 2) > 1;
na = numel(a);
nb = numel(b);
a  = [zeros(max(1, nb - na + 1), 1); a(:)];  % Pad with at least one zero
b  = [zeros(max(1, na - nb + 1), 1); b(:)];
c  = a + b;  % Standard addition
carry = 0;   % Shift the values above 10
for k = numel(c):-1:1
  cc    = c(k) + carry;
  c(k)  = rem(cc, 10);
  carry = (cc - c(k)) / 10;  % Must be integer
end
if c(1) == 0       % Crop leading zero
  c = c(2:numel(c));
  % If wanted crop all leading zeros:
  % c = c(find(c, 1):numel(c));
end
if isrow % Reply a row vector if input "a" was one
  c = c.';
end
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