Filling up a vector

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alpedhuez
alpedhuez 2018-3-27
评论： Stephen23 2018-4-2
Suppose I have 1 by 2N vector
x=zeros(1,2*N);
Now I have N of 1 by 2 vector
y1=ones(1,2), y2=ones(1,2)
and I want to fill x as
[y1 y2 ...]
what will be a compact way to fill x in this way (instead of concatenation)?
  1 个评论
Stephen23
Stephen23 2018-4-2
Do NOT do this! The MATLAB documentation specifically advises against what you are trying to do: "A frequent use of the eval function is to create sets of variables such as A1, A2, ..., An, but this approach does not use the array processing power of MATLAB and is not recommended. The preferred method is to store related data in a single array"
source: https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html
Read this to know more:
http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

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回答（1 个）

Walter Roberson
Walter Roberson 2018-3-27
x(1:2:end) = y1;
x(2:2:end) = y2;
or
x = reshape([y1; y2], 1, []); %requires that y1 and y2 be row vectors
or
x = reshape([y1(:), y2(:)].', 1, []); %does not requires that they be row vectors
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Walter Roberson
Walter Roberson 2018-3-28
编辑：Walter Roberson 2018-3-28

http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Though I see now that I misinterpreted your question -- I thought you wanted alternating elements, but instead you were looking for dynamic variable names.

alpedhuez
alpedhuez 2018-3-28
Let me think about it and phrase questions in a clearer way. Thank you.

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