Problems with for loop

Hi,

I've a column vector q with 137 elements. I want generate a row vector Q

Q=[q(i) 0] taking elements of q one by one. I've tried by a for loop in this way:

for i=1:137
Q=[q(i) 0];
end

but it returns only the last element of q. This's q(137) in Q.

How can i set it for all elements of q ?

Answer 1

[Andrei Bobrov]

more

Q = zeros(1,2*length(q));
Q(1:2:end) = q

Answer 2

[Walter Roberson]

Q = reshape([q(:),zeros(numel(q),1)],1,[]);

or

Q = q(:);
Q(1,2) = 0;  %expands to 2 columns
Q = reshape(Q,1,[]);  %row vector

[Sean de Wolski]

I think you need to transpose Q before the reshape.

Q = reshape(Q.',1,[]);

[Walter Roberson]

Ah, you are right. Okay, that leads to

Q = q(:).';

Q(2,1) = 0;

Q = reshape(Q,1,[]);

or

Q = reshape([q(:),zeros(numel(q),1)].',1,[]);

[Walter Roberson]

or

Q = reshape([q(:).';zeros(1,numel(q))],1,[]);

Answer 3

[Sean de Wolski]

To fix this you would need:

for ii = 1:137 %don't use i, it's the sqrt(-1)
 Q(ii*2-1:ii*2) = [q(ii) 0];
end

Walter's solution is the best way to do this, however.

Answer 4

[cyberdyne]

Thanks at all !!! ^^