how to compare string array with the names of structure's fields.

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Sara 2018-7-2

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评论： Sara 2018-7-3

I have a structure with 12 fields and a string array named variables containing 4 values. I want to compare all values in my string arrays with the names of my structure fields, and if the fields' name and the string value were the same, return values of that field as an output. I try strcmp command to compare my string array with the fields' name in a for loop.(for i = 1:numel(variables)) then I use switch and case but I have no idea how to return the field values as an output when the statement is true. (I think I should use getfield command but I don't know how). could you please help me in this regard. thank you.

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Adam 2018-7-2

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You can use dynamic strings to get data out of a struct field e.g.

str = 'SomeStructFieldName';
value = myStruct.( str );

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Answer 1

Paolo 2018-7-2

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 S.a = {'First field'};
 S.b = {'Second field, entry 1','Second field,entry 2'};
 S.c = {1,2,3};
 mystring = {'a','game','matlab','c'};
 [~,indx] = ismember(fieldnames(S),mystring);
 all = arrayfun(@(x) getfield(S,mystring{x}),indx(indx>0),'un',0);

all{:} =

 {'First field'}
 {[1]}    {[2]}    {[3]}

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Stephen23 2018-7-3

编辑：Stephen23 2018-7-3

@Sahar: the @(x) defines an anonymous function in x:

https://www.mathworks.com/help/matlab/matlab_prog/anonymous-functions.html

Paolo 2018-7-3

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 T = table(all{:});
 T.Properties.VariableNames = mystring(indx(indx>0));
 T =
1×2 table
          a                  c        
    _____________    _________________
    'First field'    [1]    [2]    [3]

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Answer 2

Stephen23 2018-7-3

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编辑：Stephen23 2018-7-3

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I would use struct2cell to get a cell array, then used basic MATLAB indexing to obtain the "fields" (rows of the cell array) that you want. Using a cell array makes it easy to use cell2table to generate a table from the cell array and the fieldnames:

>> S.a = '1st';
>> S.b = {'2ndOne','2ndTwo'};
>> S.c = 3;
>> F = fieldnames(S);
>> C = struct2cell(S);
>> lookfor = {'a','hello','world','c'};
>> [idx,idy] = ismember(lookfor,F);
>> idz = idy(idx)
>> T = cell2table(C(idz,:),'VariableNames',F(idz))

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Stephen23 2018-7-3

编辑：Stephen23 2018-7-3

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@Sahar: you are right, I think the first input needs to be transposed:

Table = cell2table(Cell(indz,:).','VariableNames',Fname(indz));

According to the cell2table help "Each column of C provides data for a table variable", whereas struct2cell returns one row for each field, so a transpose is required.

Sara 2018-7-3