Add a vector to a struct array

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Frank 2014-8-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/151832-add-a-vector-to-a-struct-array

编辑： Sean de Wolski 2014-8-22

I have a struct array, say

a(1).b=1
a(2).b=1
a(1).c=1
a(2).c=1

and an vector, say

c=[1 2]

Now I want to add vector c to a, in order to obtain something like a.c

How can I do this without a for-loop? (actually the length of the struct is not 2, but thousands)

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Answer 1

Sean de Wolski 2014-8-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/151832-add-a-vector-to-a-struct-array#answer_149429

编辑：Sean de Wolski 2014-8-21

在 MATLAB Online 中打开

You could use a for-loop (which would be the easiest to understand) and may be the fastest. Or you could use comma-separated list expansion which is trickier.

a(1).b=1
a(2).b=1
a(1).c=1
a(2).c=1
c = [pi exp(1)];
c = num2cell(c)
[a(:).c] = c{:}
a.c

Frankly, I would recommend avoiding this structure altogether. Why not have a 1x1 struct with a field c which is a 1xn?

a.c = [1 2]
a.c(2)

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Frank 2014-8-21

Thank you.

As for avoiding this structure: I recognized in the meantime, that there is more overhead when using the struct arrays. But the struct arrays are part of a major legacy Matlab program, and I have to live with it for the moment.

As far as I know it is good Matlab practise to avoid for-loops due to low speed, so I hoped there is a single command to shuffle vector data into struct arrays. But now it appears that it might not be possible.

Sean de Wolski 2014-8-22

编辑：Sean de Wolski 2014-8-22

That's exactly what my first approach does! It uses comma separated list expansion (instead of a for-loop) on both the left and right hand side to distribute the elements.

Of course MATLAB is plenty fast with loops and has been for a while.

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