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Problems with for loop

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cyberdyne
cyberdyne 2011-6-3
关闭： MATLAB Answer Bot 2021-8-20
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 ?

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回答（4 个）

Andrei Bobrov
Andrei Bobrov 2011-6-3
more
Q = zeros(1,2*length(q));
Q(1:2:end) = q
Walter Roberson
Walter Roberson 2011-6-3
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
  3 个评论
显示 1更早的评论
Walter Roberson
Walter Roberson 2011-6-3
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
Walter Roberson 2011-6-3
or
Q = reshape([q(:).';zeros(1,numel(q))],1,[]);
Sean de Wolski
Sean de Wolski 2011-6-3
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.
cyberdyne
cyberdyne 2011-6-4
Thanks at all !!! ^^

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