"so there is no way to have the output vector with directly length of 5 ?"
Of course there are multiple ways to achieve this, here is probably the best one (based on the principal that in general it is easiest to loop over indices 1:N, rather than over some special values):
x = [2:10,55,20]
y = zeros(5,1);
v = 3:7;
for k = 1:numel(v) % this is usually better
y(k) = x(v(k)) + 3;
end
display(y)
"I need to have the loop starting from 3"
I recommend avoiding doing that, but if you really must (hopefully not for reasons related to DIR):
y = zeros(5,1);
z = 0;
for k = 3:7
z = z+1;
y(z) = x(k)+3;
end
display(y)
Of course using a loop is not very good use of MATLAB, better would be simply:
y = x(v).' + 3
"...after prelocation will be zeros and I do not wanna remove them with y (y==0) =[] any ideas ??"
I just showed you three approaches. Not hard at all.
