How can I access part of my stucture by index?

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bkshn
bkshn 2015-2-13
编辑： Stephen23 2015-2-14
Hello
I have a structure like bellow
x.part1.vector=3;
x.part1.cost=4;
x.part2.vector=5;
x.part2.cost=6;
x.part3.vector=7;
x.part3.cost=8;
I want to access value of vector on part (for example 3).
How can I access this by index?
thanks for your help

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采纳的回答

Image Analyst
Image Analyst 2015-2-13
bkshn, try this and see if it's what you want:
% Define an array of structures.
x(1).vector=3;
x(1).cost=4;
x(2).vector=5;
x(2).cost=6;
x(3).vector=7;
x(3).cost=8;
% Access "part 3" with an index
index = 3;
output = x(index).vector
% Sum all "vector" fields for all indexes ("parts"):
outputSum = sum([x.vector])

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Stephen23
Stephen23 2015-2-13
编辑：Stephen23 2015-2-14
What you have defined is a scalar structure. This does not support indexing because there is only one structure element. You can access the data only using the fieldnames.
If you wish you use indexing, then you can create a non-scalar structure, which you can then use indexing with. There a multiple ways to create a non-scalar structure . Here are two ways of creating the same non-scalar structure:
>> A(1).data = 4;
>> A(2).data = 5;
>> A(3).data = 6;
OR
>> A = struct('data',{4,5,6});
And then access the field of any element of the structure using indexing and the fieldname:
>> A(2).data
ans = 5
Which means you can get the sum of all of the elements using this simple code:
>> sum([A.data])
ans = 15
  1 个评论
bkshn
bkshn 2015-2-13
I do it because I want to have a vector and the sum of its value in a structure.
then I want to select the vector with minimume sum of value.
I think I can't do it by your example. Am I right?

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