Add a vector to a struct array

2014 8 21
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更新时间：2014 8 22
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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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Sean de Wolski
Sean de Wolski 2014-8-21
编辑：Sean de Wolski 2014-8-21

1 个投票

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
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
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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