Loop over fieldnames in a matlab structure
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Dears,
I have a MatLab "struct", with different "level" and "sub-structures". When printed to a cell, the data contained in the "struct", look like that:
report.COUNTRY.SOURCE.SCENARIO.CATEGORY.ENTITY = YEAR YEAR ...;
In order to produce tables listing the different variables combinations, I would like to loop over the fieldnames contained within the "struct".
I am currently trying to write a function able to do that:
fields=fieldnames(struct);
for categoryidx=1:length(fields)
categoryname=fields{categoryidx};
if isstruct(struct.(categoryname))
category=fieldnames(struct.(categoryname));
for entityidx = 1:length(category);
entityname = category{entityidx};
if isstruct(struct.(categoryname).(entityname))
gases=fieldnames(struct.(categoryname).(entityname));
end
end
end
end
Unfortunately, this is just producing anything! Does anyone has any idea how to loop over fieldnames in such a matlab structure? Thank you!
0 Kommentare
Antworten (3)
Titus Edelhofer
am 11 Aug. 2015
Hi David,
generally speaking you seem to know how to loop on fieldnames ... I'm not sure now where your problem is? You can change your function to work recursively, if you don't know the number of levels, something like (note, "struct" is not an ideal variable name)
function aTable = loopovernestedstructs(aTable, aStruct)
fields = fieldnames(aStruct);
for idx = 1:length(fields)
aField = aStruct.(fields{idx});
if isstruct(aField)
aTable = loopovernestedstructs(aTable, aField);
else
% add to the table what you want, e.g., if it's a number:
aTable(end+1) = aField;
end
end
Hope this helps,
Titus
2 Kommentare
Titus Edelhofer
am 13 Aug. 2015
Bearbeitet: Titus Edelhofer
am 13 Aug. 2015
Hi David,
maybe you can give a simple example, how it looks like, e.g.
report.USA.Reut.Scen01.Metal.Company01 = [2001 2002]; report.USA.Reut.Scen01.Metal.Company02 = [2003 2004 2005]; report.USA.Reut.Scen01.Rail.RailCompany01 = [2015];
and then how your table should look like ... ?
Then we should be able to help you out ...
Titus
Walter Roberson
am 11 Aug. 2015
That appears to be me to broadly correct to me, just incomplete as it stops analyzing at gases and does not do anything with what it finds.
Have you considered using a recursive routine? Hand it a variable and the "left" information to print out. If it detects the variable is a struct, iterate over its fields, passing the field content and the "left" information and the field name recursively into the routine. If it detects that it is working with a non-struct, print or return a report on the content.
Bill Tubbs
am 20 Feb. 2023
Bearbeitet: Bill Tubbs
am 20 Feb. 2023
There is another way to loop over the fieldnames:
for field = fieldnames(mystruct)'
if isstruct(mystruct.(field{:}))
...
end
end
The only annoying thing I find is that field is a cell not a string so to get the value you have to use the {:} notation. NOTE: It is important to transpose the fieldnames into a row vector.
I found one way to avoid this but there might be better ways:
for field = string(fieldnames(mystruct))'
if isstruct(mystruct.(field{:}))
...
end
end
2 Kommentare
Grigorii Nefedov
am 21 Jun. 2023
even
for field = string(fieldnames(mystruct))'
if isstruct( mystruct.(field) )
...
end
end
Bill Tubbs
am 21 Jun. 2023
Bearbeitet: Bill Tubbs
am 21 Jun. 2023
Yes, sorry, that is what I meant. Should I update my comment now that you have pointed this out?
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