Is there a function that will display all the fields of a nested structure in MATLAB?

I have a nested structure, containing levels of structures within it.

I would like to be able to view all the fields of this nested structure.

Answer 1

[MathWorks Support Team]

There is not a built in function in MATLAB that would display the contents of a nested structure hierarchy.

You can achieve this by writing a function that recursively navigates through each field of the structure and displays its contents.

Find attached an example file, unfold.m, which displays the contents of nested structures. The help contents of the function contain more information on its usage.

[KAE]

This is useful for looking at multi-level XML files read in by xml2struct. I wish there were more XML utilities in Matlab to make it easy to extract data from many records.

Answer 2

[Bryant]

jsonencode will at least show everything

Answer 3

[Brent F]

The printstruct script displays the MATLAB struct contents recursively:

https://www.mathworks.com/matlabcentral/fileexchange/52573-printstruct-recursively-print-structures-to-the-command-window-or-a-cell-char-array

[Justin Mulvey]

Thank you Thank you Thank you Thank you Thank you Thank you. Can't believe I finally have this tool in matlab.

[Brent F]

It's very nice, but doesn't print the value of cell arrays. See line 394:

% Print cell array information, i.e. the size of the cell array.

% (The content of the cell array is not printed.)

I quickly added these lines to show something, but it probably needs to be more general:

...

listStr = [listStr; {[strIndent ' |' filler ' ' Field ' :' varStr]}];

% Add contents of 1-d cell array (needs generalization)

for j = 1 : length(Structure.(Field))

contents = Structure.(Field);

cellStruct = struct([Field '_' num2str(j)], contents(1,j));

cellContents = recFieldPrint(cellStruct, indent, depth, printValues, maxArrayLength, structname, sortfields);

listStr = [listStr; cellContents];

end

It's unbelievable that Matlab doesn't provide this by default.

Answer 4

[Tom Tacken]

Yes, you can use disp() for this.

Answer 5

[Marcelo Moraes]

I would suggest a recursion using these functions:

Field names of structure, or public fields of Java or Microsoft COM object - MATLAB fieldnames - MathWorks Benelux

Field of structure array - MATLAB getfield - MathWorks Benelux

Answer 6

[Jessica]

Here's what I came up with.

S.Conc.HO2.wow=[1:10];
S.Met.Temp=[1:10];
S.Time=[1:400];


names= unnest_fields(S, 'S')

names = 1×3 cell array
    {'S.Conc.HO2.wow'}    {'S.Met.Temp'}    {'S.Time'}

function names= unnest_fields(S, parent, names)
    % Function to list all the non-structure aka nested fields in a struct.
    if nargin<2; parent='S'; end % structure name... 
    if nargin<3; names= {}; end % names of all non-structure fields. 
    
    fields=fieldnames(S);
    for i=1:length(fields)
        new_parent=append(parent,'.',cellstr(fields{i}));
        
        if ~isa(S.(fields{i}),'struct') 
            % If this subfield isn't a structure then save "new_parent" to
            % the output list of un-nested field names. 
            names=horzcat(names,new_parent);
        else
            % Otherwise recursively look into this one... with "new_parent".
            names= unnest_fields(S.(fields{i}),new_parent, names);
        end
    end
end

[Stephen23]

Nice work, you should make a note that it only works for scalar structures.

[Willingo]

One could just call any index of the struct array then.

Or one could just continue to use the original function above and use arrayfun on the struct

Note that this may or may not "fail" if you have the same field name at different levels of the struct. You might want to use unique(names) or maybe store the level alongside the names.

Lots of options.

function names= unnest_fields(S, parent, names)
    % Function to list all the non-structure aka nested fields in a struct.
    if nargin<2; parent='S'; end % structure name... 
    if nargin<3; names= {}; end % names of all non-structure fields. 
    
    %% My edits
    switch isscalar(S)
        case 1
        case 0
            S = S(1);
        otherwise
            error("Impossible")
    end
    %% end my edits
    
    fields=fieldnames(S);
    for i=1:length(fields)
        new_parent=append(parent,'.',cellstr(fields{i}));
        
        if ~isa(S.(fields{i}),'struct') 
            % If this subfield isn't a structure then save "new_parent" to
            % the output list of un-nested field names. 
            names=horzcat(names,new_parent);
        else
            % Otherwise recursively look into this one... with "new_parent".
            names= unnest_fields(S.(fields{i}),new_parent, names);
        end
    end
end