MATLAB: How to add element to a cell array struct without loop

cell arrays structurewithout loop.

Hi, I have a cell array, each of them is a structure, I want to add values in all arrays with field name myfield, how I do it without a loop?

for i = 1:10
   C{i}.myfield = 1;
end

I can not use

 C{1:10}.myfield = 1;

because it has the error:Expected one output from a curly brace or dot indexing expression, but there were 10 results. Maybe is there another simple method?

Thanks forward

Best Answer

This would be trivially easy if you had stored your data in a non-scalar structure (instead of inefficiently in lots of separate structures in a cell array):

>> [S(1:10).data] = deal(1)
S = 
1x10 struct array with fields:
    data
>> S(1).data
ans =
     1
>> S(6).data
ans =
     1

Related Solutions

MATLAB: How to extract data from a cell array which contains structs

Something like this might work for you:

cell2mat(cellfun(@(s)s.field,C,'uni',0))

it assumes that the data is able to be concatenated into one array, and that the structures are scalar. You will need to use the correct fieldname, and orient the input cell array and its contents to suit your data (you did not give any info about this). Here is an example:

>> C{1,1} = struct('A',1:3);
>> C{2,1} = struct('A',4:6);
>> C{3,1} = struct('A',7:9);
>> cell2mat(cellfun(@(s)s.A,C,'uni',0))
ans =
   1   2   3
   4   5   6
   7   8   9

"Is there a better way?"

This task would be much simpler if you simply used one non-scalar structure, then you could simply do this:

cat(1,S.field)
[S.field]
vertcat(S.field)
etc.

For example:

>> S(1).A = 1:3;
>> S(2).A = 4:6;
>> S(3).A = 7:9;
>> vertcat(S.A)
ans =
   1   2   3
   4   5   6
   7   8   9

Do you see how much simpler the code is, because I stored the data in a much better way?

MATLAB: How to create a cell array with struct elements

repmat({struct('myfield',{})}, 2, 7)

Note the correction of struct('myfield',[]) to struct('myfield',{}). The version you had, with [], is for a 1 x 1 struct with a field that is initialized to []. The version with {}, creates a 0 x 0 struct with the field defined in its template but with no content. An "empty structure" should have have 0 as one of its dimensions or else it is not actually empty.

Best Answer

Related Solutions

MATLAB: How to extract data from a cell array which contains structs

MATLAB: How to create a cell array with struct elements

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