How do I rename fields of a structure array?

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John Petersen
John Petersen 2016-3-17
评论： Leon 2024-3-9
Say I have a structure array such as
A =
1x49 struct array with fields:
a
b
c
d
How do I rename the structure fields? Such as
A =
1x49 struct array with fields:
aa
ba
ca
da
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Steven Lord
Steven Lord 2024-1-9
编辑：Steven Lord 2024-1-9
To officially submit this as an enhancement request please contact Technical Support directly using this link. When you do, please mention the circumstances in which you'd want to use this functionality if it existed.
  • Would you need it to support non-scalar struct arrays?
  • Would you need it to be able to rename one field at a time or renaming a collection of fields all at once?
  • How would you expect it to operate if you tried to rename a field to a field name that already exists in the struct? Error, warn and do nothing, overwrite, try to merge them somehow, etc.?
  • Do you need it to be able to operate over multiple levels? If you had a struct a with fields b and c where b was itself a struct array with field d, would you expect to be able to change both a.c and a.b.d in one call (assuming the answer to my second question was "renaming a collection of fields all at once")?

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采纳的回答

Walter Roberson
Walter Roberson 2016-3-17
struct2cell( cell2struct(A), {'aa', 'ba', 'ca', 'da'})
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Guillaume
Guillaume 2016-3-18
编辑：Guillaume 2016-3-18
This is probably the most straightforward method. For safety, as there's no guarantee that the fields in the original structure are ordered alphabetically, I'd use:
cell2struct(struct2cell(ordefields(A)), {'aa', 'ba', 'ca', da'})
Note that this will cope with structure arrays as well.
Christian Svensson
Christian Svensson 2019-11-27
编辑：Christian Svensson 2019-11-27
I encountered this problem recently, for completeness I'll add my solution. Assuming that you want to add the same suffix to all fieldnames, you can use
cell2struct(struct2cell(A), strcat(fieldnames(A), 'a'))
Note that fieldnames and struct2cell return the field names and the values in the same order, so no sorting is needed.

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更多回答（6 个）

Jos (10584)
Jos (10584) 2016-3-17
There is a somewhat hidden function called renameStructField, that can do the job, perhaps within a loop.
Or use dynamic field names and copy the fields into a new structure. This makes code quite readable and bug proof.
oldnames = {'a','b','c'}
newnames = {'aa','test','cXY'}
for k=1:number(oldnames)
Snew.(newnames{k}) = Sold.(oldnames{k}) ;
end
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John Petersen
John Petersen 2016-3-17
Right, this does not work for a structured array. Do you know what 'tweaking' would make it work?

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Sriram Nayak
Sriram Nayak 2020-4-18
编辑：Walter Roberson 2024-3-6
function structOut = renamefield(structIn, oldField, newField)
for i = 1:length(structIn)
structIn = setfield(structIn,{i},newField,getfield(structIn(i),oldField));
end
structOut = rmfield(structIn,oldField);
end
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Walter Roberson
Walter Roberson 2024-3-6
This will fail if the new field names happen to include some of the old field names. For example
a -> aa
b -> a

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Jos (10584)
Jos (10584) 2016-3-18
You can use DEAL and a for-loop to change fieldnames:
% create a structure array, with different fields
for k=1:10,
Sold(k) = struct('a',k,'b',1:k','c',sprintf('test%02d',k)) ;
end
% engine
oldnames = {'a','b','c'}
newnames = {'aa','test','cXY'}
N = numel(Sold)
for k=1:numel(oldnames)
[Snew(1:N).(newnames{k})] = deal(Sold.(oldnames{k})) ;
end
Teresa Martinez
Teresa Martinez 2021-5-26
Create new fields with the same data:
A.aa = A.a;
A.ba = A.b;
and remove the old ones:
A = rmfield(A,'a');
A = rmfield(A,'b');
Jan
Jan 2022-6-8
Although this thread is old, it has a lot of views and it is worth to mention this implementation as fast C-Mex:
https://www.mathworks.com/matlabcentral/fileexchange/28516-renamefield
Leon
Leon 2024-1-7
编辑：Leon 2024-1-7
Until Matlab (hopefully) introduces a rename field function, I would convert to a table then use renamevars() and then convert back to a struct. E.g., where S is your struct:
T = struct2table(S);
T = renamevars(T, 'Old_Name', 'New_Name');
S = table2struct(T);
Or, as one line:
S = table2struct(renamevars(struct2table(S), 'Old_Name', 'New_Name'));
An advantage of this over converting to a cell array and back is that you don't need to worry about the names of the other fieldnames, or know what number the field is, etc. You can still rename several fields at once when using renamevars. Also, since each variable in a Matlab table has to maintain the same value for all rows, it should be much more efficient memory-wise than converting a large struct into a cell array and back (where each cell can be of any type and that type must be stored), but I haven't done any tests.
Actually, once you have converted to a table, you may want to have a good think about whether it makes sense to convert it back into a struct: it is often more comfortable to work with tables, and they can be more efficient memory-wise. Apart from better memory use and functions like renamevars, there are neat features like being able to have several variable names under one column.
Or try the C-Mex "renamefield" on Matlab file exchange, as Jan suggested.
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Stephen23
Stephen23 2024-3-9
"I'm surpised Matlab isn't smart enough to just keep the columns as cell type."
They aren't cell type.

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