Vertical concatenation of structure fields (compact form)

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Massimiliano Zanoli
评论： Massimiliano Zanoli 2020-10-8
Hi,
I know there is a similar question but it's not about the compact form.
My question is: why does the following not result in a vertical concatenation? (it also fails for numerical values)
Or, how can I change it to concatenate vertically into ['value_1' ; 'value_2'] ?
Thanks!
>> structure(1, 1).field = 'value_1';
>> structure(2, 1).field = 'value_2';
>> [structure(:, 1).field]
ans =
'value_1value_2'
>>

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采纳的回答

Stephen23
Stephen23 2020-10-8
编辑：Stephen23 2020-10-8
Your example concatenates horizontally because it is exactly equivalent to doing this:
[structure(1).field,structure(2).field]
which is just shorthand for
horzcat(structure(1).field,structure(2).field)
If you want to concatenate vertically, use either of these
vertcat(structure.field)
cat(1,structure.field)
For more information on how to use comma-separated lists:
https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html
https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists
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Stephen23
Stephen23 2020-10-8
Comma-separated arrays are equivalent to values separated by commas, not by semi-colons. So this:
structure.field
is equivalent to
structure(1).field,structure(2).field, .. ,structure(end).field
by the very definition of comma-separated lists. There is no equivalent syntax for semi-colon-separated lists.
Massimiliano Zanoli
Massimiliano Zanoli 2020-10-8
I agree, but (:, 1) should indicate vertical arrangement. That [] defaults to horzcat is a choice, not a must.

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更多回答（2 个）

Bjorn Gustavsson
Bjorn Gustavsson 2020-10-8
This gets you to a 2-by-suitable char array:
char(structure.field)
But this will obviously not be a general solution for fields of different data-types.
HTH
Ameer Hamza
Ameer Hamza 2020-10-8
By default [] is equivalent to horizontal concatination hozcat(). Use vertcat() for vertical output
vertcat(structure.field)

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