How can I mix two arrays?

7 vues (au cours des 30 derniers jours)
Alex Strongholm
Alex Strongholm le 15 Jan 2015
Modifié(e) : Stephen23 le 18 Jan 2015
Given A=[1 3 5 7 9] and B=[2 4 6 8], how can I create C=[1 2 3 4 5 6 7 8 9]?

Réponse acceptée

Youssef  Khmou
Youssef Khmou le 15 Jan 2015
Modifié(e) : Youssef Khmou le 15 Jan 2015
This question is general due to the variation of array dimensions, however for a particular case you described, vectors A and B can be mixed by single loop, so the following scheme is valid only when dim(A)=dim(B)+1 as in the example :
A=[1 3 5 7 9];
B=[2 4 6 8];
n=min(length(A),length(B));
C=[];
for t=1:n
C=[C A(t) B(t)];
end
C=[C A(end)];
  3 commentaires
Stephen23
Stephen23 le 15 Jan 2015
Modifié(e) : Stephen23 le 18 Jan 2015
This answer is very poor use of MATLAB.
The use of a for loop and concatenating scalar values onto the end of with every iteration is poor coding practice in MATLAB. If the arrays are large, then this will be slow as MATLAB keeps expanding the array and copying it to new memory. One solution is to preallocate the array.
For a much neater and simpler solution see my answer below.
Stephen23
Stephen23 le 15 Jan 2015
Modifié(e) : Stephen23 le 15 Jan 2015

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Plus de réponses (1)

Stephen23
Stephen23 le 15 Jan 2015
Modifié(e) : Stephen23 le 16 Jan 2015
This can be done simply using indexing, without any loops:
>> A = [1,3,5,7,9];
>> B = [2,4,6,8];
>> C(1:2:2*numel(A)) = A;
>> C(2:2:end) = B
C =
1 2 3 4 5 6 7 8 9
This solution also assumes that numel(A)==numel(B)+1.
Most importantly, for larger arrays this code will be much faster than the accepted solution, so it is the most universal solution.

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