What is wrong with my code ?

function coded = caesar(a,b);
x = length(a);
y = double(a);
for i = 1:x
    y(i) = y(i) + b;
if y(i) > 126;
    j = y(i)- 126;
    y(i) = 31+j;
elseif y(i) < 32;
    j = y(i) - 32;
    y(i) = 127+j;
end
coded(i) =char(y(i));
end
end 

[Walter Roberson]

What error do you observe?

It does feel a bit odd that newline (character position 10) is mapped to 'i' (lower-case I) when b is 0, but without specifications, we do not know that it is wrong.

Note that your function can emit characters beyond ~ if your input is ß (223) or beyond