What is the best practice to recursively extract data from a nested structure in matlab?
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Moon Diver
am 12 Jan. 2022
Kommentiert: Moon Diver
am 14 Jan. 2022
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
4 Kommentare
Stephen23
am 12 Jan. 2022
Bearbeitet: Stephen23
am 12 Jan. 2022
@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.
Akzeptierte Antwort
Stephen23
am 12 Jan. 2022
Bearbeitet: Stephen23
am 12 Jan. 2022
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.alt
Z.nump1.list
Z.nump2.list
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
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