What is the best practice to recursively extract data from a nested structure in matlab?

I'm trying to exctract some data from a nested structure in a recursive manner. First, I know that this has a field (values) which repeats itself inside the nested structure. Secondly I know that the structure which has those values has only structures as fields. In the below code I've tried to acces the structure.values by searching if my current structure has a field named values. If it has I put .values at the end of my structure name. If it doesn't have this field, I verify if all the fields are structures. If the are it means that I will have to consider them further and to extract the values from each one. If the fields are not structures it means that they are values and I save them into a new simplified structure.( Example of fields that I want(S.values.model1.values.mission.values.(alt/list) Currently, with the bellow code I'm only able to get the values from one field and then I get an error and don't know how to approach further.

Code example:

clear all
clc

S=struct()

S.case='1';
S.type='A';
S.values.model1.case='2'
S.values.model1.type='C'
S.values.model1.values.mission.case='3'
S.values.model1.values.mission.type='D'
S.values.model1.values.mission.values.alt='none'
S.values.model1.values.mission.values.list=2
S.values.model1.values.mission.values.parameter=4

S.values.model1.values.phase.case='4'
S.values.model1.values.phase.type='A'
S.values.model1.values.phase.values.num='all'
S.values.model1.values.phase.values.eq=2
S.values.model1.values.phase.values.unit=4

S.values.model1.values.analysis.case='1'
S.values.model1.values.phase.type='A'
S.values.model1.values.phase.values.nump1.list='all'
S.values.model1.values.phase.values.nump1.table='four'
S.values.model1.values.phase.values.nump1.mean=0

S.values.model1.values.phase.values.nump2.list='none'
S.values.model1.values.phase.values.nump2.table='three';
S.values.model1.values.phase.values.nump2.mean=1


s=S.values.model1;
names=fieldnames(s);
nnames=numel(names);

newStruct={};
[valsi,newstructi]=extractValues(names,s,nnames,newStruct)


function [vals,newStruct]=extractValues(names,vals,nnames,newStruct)
if any(strcmp(names,'values'))
    vals=vals.('values');
    names=fieldnames(vals)
    nnames=numel(names)
    
    [vals,newStruct]=extractValues(names,vals,nnames,newStruct);
   
end


for j=1:nnames
    
    value(j)=isstruct((vals.(names{j})));
end

if all(value)
    
    
    for k=1:nnames
        
        vals=(vals.(names{k}));
        names=fieldnames(vals);
        nnames=numel(names);
        
        [vals,newStruct]=extractValues(names,vals,nnames,newStruct);
        
    end
    
else
    
    for j=1:nnames
        
        value=(vals.(names{j}));
        newStruct.(names{j})=value;
    end
end
end

[Stephen23]

Please show us the expected output for that given input structure. This is more useful that trying to reverse-engineer non-functioning code.

[Moon Diver]

For example, from the structure S, I want to obtain a new structure with the following parameters:

.mission.values.alt (Newstruct.alt)

.mission.values.list (Newstruct.list)

.mission.values.parameter (Newstruct.parameter)

.phase.values.num (Newstruct.num)

.phase.values.eq (Newstruct.eq)

.phase.values.unit (Newstruct.unit)

phase.values.nump1/nump2.list,table, mean

[Stephen23]

@Moon Diver: your description does not sufficiently explain the rules for deciding which text (or numeric, etc) to store. The confusion occurs because the 'values' field can occur repeatedly at multiple levels of nesting.

Consider these two cases:

S.values.model1.values.phase.type='A'
S.values.model1.values.phase.values.nump1.list='all'

Note that in both cases, the text is nested at the same depth below the 'values' field. If we align them to the text, this becomes clearer:

             S.values.model1.values.phase.type='A'   % you don't want this
S.values.model1.values.phase.values.nump1.list='all' % but you want this
%                            ^^^^^^                  values
%                                   ^^^^^            one
%                                         ^^^^       two
%                                              ^^^^  text

Unless you are also considering the depth of structure nesting (which so far you have not shown or mentioned), then how do you distinguish between these two cases, which have completely identical levels of nesting between the text value and the 'value' field? Why do you store one, but not the other? Please explain the logic.

[Moon Diver]

I get them this way with the mention that I need to extract de values from the last values field. Not really a logic thing, but those are the instructions.

Answer 1

[Stephen23]

S=struct();
S.case='1';
S.type='A';
S.values.model1.case='2';
S.values.model1.type='C';
S.values.model1.values.mission.case='3';
S.values.model1.values.mission.type='D';
S.values.model1.values.mission.values.alt='none';
S.values.model1.values.mission.values.list=2;
S.values.model1.values.mission.values.parameter=4;
S.values.model1.values.phase.case='4';
S.values.model1.values.phase.type='A';
S.values.model1.values.phase.values.num='all';
S.values.model1.values.phase.values.eq=2;
S.values.model1.values.phase.values.unit=4;
S.values.model1.values.analysis.case='1';
S.values.model1.values.phase.type='A';
S.values.model1.values.phase.values.nump1.list='all';
S.values.model1.values.phase.values.nump1.table='four';
S.values.model1.values.phase.values.nump1.mean=0;
S.values.model1.values.phase.values.nump2.list='none';
S.values.model1.values.phase.values.nump2.table='three';
S.values.model1.values.phase.values.nump2.mean=1;

Z = mainfun(S)

Z = struct with fields:
          alt: 'none'
         list: 2
    parameter: 4
          num: 'all'
           eq: 2
         unit: 4
        nump1: [1×1 struct]
        nump2: [1×1 struct]

Z.alt

ans = 'none'

Z.nump1.list

ans = 'all'

Z.nump2.list

ans = 'none'

function B = mainfun(A)
B = struct();
nestfun(A,{})
    function nestfun(D,C)
    if isstruct(D)
        F = fieldnames(D);
        for k = 1:numel(F)
            if nnz(strcmpi(C,'Values'))==3
                B.(F{k}) = D.(F{k});
            else
                nestfun(D.(F{k}),[C,F(k)])
            end
        end
    end 
    end
end