MATLAB: Removing structure field if

isfieldremove fieldstructure

Hello,

I have two structures with a different number of fields. Struct1 has 75 fields and Struct2 has 111 fields. I would like to remove the fields from Struct2 that have a fieldname that is not equal to any of the field names in Struct1 so the two structures have the same number of fields with same field names. Alternatively I'd like to create a new structure that only has the fields from Struct2 that have field names equal to Struct1. I've tried for-if loops using 'isfield' and 'rmfield' and so on but I haven't managed to get anything to work yet. I'd really appreciate any help!

Best Answer

fn1 = fieldnames(Struct1);
fn2 = fieldnames(Struct2);
tf = ismember(fn2, fn1);
NewStruct = struct();
for K = 1 : length(tf)
  if tf(K); NewStruct.(fn2{K}) = Struct2.(fn2{K}); end
end

I expect that is also a vectorized formulation that uses struct2cell()

Related Solutions

MATLAB: Multiplying structures together based on field names

A function to multiply two structures field by field. This needs to be copied into a file on your MATLAB path called multiplyStructs.m

function s3 = multiplyStructs(s1, s2)
%MULTIPLYSTRUCTS multiplies structures field by field
%   S3 = MULTIPLYSTRUCTS(S1, S2) returns a structure S3 with those fields
%   that are common to S1 and S2. The value of each such field is the
%   matrix product of the values of the corresponding fields of S1 and S2.
% get common field names
f1 = fieldnames(s1);
fnames = f1(ismember(f1, fieldnames(s2)));
% multiply
for k = 1:length(fnames)
    fname = fnames{k};
    s3.(fname) = s1.(fname) * s2.(fname);   % matrix product
end
end

Test code:

struct1.a = 1;
struct1.b = 2;
struct1.c = 3;  % will be ignored as no match
struct1.d = 4;
struct2.a = 3;
struct2.b = 4;
struct2.d = 10;
struct3 = multiplyStructs(struct1, struct2)

An alternative way, which works only if all the structures have the same fields, but which generalises more readily to multiple structures, is to use this function:

function s = structProd(svec)
%STRUCTPROD returns the field-by-field products of a structure array
%   S = STRUCTPROD(SARR) takes a structure array and returns a scalar
%   structure with the same fields. The value of each field of S is the
%   product of the values of the corresponding fields of SARR, which must
%   all be numerical scalars.
%
%   See also: prod
fnames = fieldnames(svec);
for k = 1:length(fnames)
    fname = fnames{k};
    s.(fname) = prod([svec.(fname)]);
end
end

and then put the structures into an array (which indeed might be the best way to store them to start with. Here's the test code:

struct1.a = 1;
struct1.b = 2;
struct1.d = 4;
struct2.a = 3;
struct2.b = 4;
struct2.d = 10;
struct3.a = -1;
struct3.b = -1;
struct3.d = -1;
struct4.a = 4;
struct4.b = 1;
struct4.d = 2;
struct5 = structProd([struct1 struct2 struct3 struct4])

MATLAB: Converting nested “summary” structure to table

Here's the loop version. There may be another way, but I didn't have any luck fighting with Matlab's tricky multiple-cell return behaviour

% create minimal test structure
mystruct.Days_from_development = struct('size',[118,1],'Type','double');
mystruct.HIV = struct('size',[52,3],'Type','string');
% get a list of all the fieldnames (i.e. substructures, i.e. names of tables)
table_names = fieldnames(mystruct);
% loop over substructures
for ind=1:length(table_names)
    % get the string for each substructure's name
    tmp = table_names{ind};
    % dump the substructure to a table row
    % by turning it into a 1xN cell array and putting the substructure string as the first cell
    mytable(ind,:) = cell2table([{tmp} struct2cell(mystruct.(tmp))']);
end
% rename the table variables appropriately
mytable.Properties.VariableNames = [{'table_name'};fieldnames(mystruct.(tmp))]

Best Answer

Related Solutions

MATLAB: Multiplying structures together based on field names

MATLAB: Converting nested “summary” structure to table

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