Assign an array of structs to a cell

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Jerry Olup 2017-11-16

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评论： Jerry Olup 2017-11-17

Hi, I have a variable sized array of structs that I read and want to assign to cell within a cell array. I found a results for "Conversion to cell from struct is not possible." in prior questions but that maps a single struct to a single cell. I would like to be able to store an array of structs to a cell. Is that possible? How? Thanks, Jerry

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Stephen23 2017-11-17

在 MATLAB Online 中打开

Jerry's "Answer" moved here:

Hi Rik, thanks for the quick response.

I believe this to be the gist of the code that I am using. Meanwhile I found a workaround by using a struct of structs... so if this isn't possible, the problem is essentially solved from my end. Even if it's not exactly the way I intended.

% final try was to allocate sufficient space for the worst case struct growth
% (I have some that are 973 ... up to 11869)
%carray = cell(11869,4);
% first try for carray
carray = cell(1,4); % 'results' assigned to 1 of 4 cells
for k = 1:4
    file1 = some_data{k}; % grab from file
    for i = 1:1000
        % gather results in array of structures
        results(i).rvr_time = str2num(file1{i,1});
        results(i).chan     = str2num(file1{i,2});
               ...
    end
    % Assign array of structs to a cell in carray
    carray{:,i} = results;
    % I tried this first:
    carray{i} = results; 
    % and this...
    carray(i) = results;
end

What happens as I iterate through the four 'files' is that the cell array grows from 1x973 (first dataset) to 1x11869 (for the third), then the fourth (1x364) is lost... ending up with a carray of 1,11869 of garbage...

thanks again, Jerry

Jerry Olup 2017-11-17

Stephen, >> Beginners often import data as string because they do not use the importing tools very effectively.

Ah, regarding importing of data:

The data is mixed between numbers (all modes, literally) and strings. It is also variable length with fields missing or having a few modes (including numeric or string, causing decisions in interpretation). That's why I ran it all as strings (with a lot, hence the ..., of code omitted). from that I can parse variations of the file effectively.

This imports all data in a few mins, so I am satisfied with the performance.

It's not regular or academic data...!

The code excerpts are meant to point out that this is storing an array of structs into a single cell.

Thanks, Jerry

Stephen23 2017-11-17

编辑：Stephen23 2017-11-17

在 MATLAB Online 中打开

"However I am trying to assign an array of structures to a single cell."

I still do not see what the problem is. Any variable can be allocated to a cell, the fact your structure is non-scalar is irrelevant. Here is a non-scalar structure array being allocated to a cell:

>> S(1).data = 1;
>> S(2).data = 3;
>> C{1} = S;

That test code throws no errors, no problems doing exactly what you state: "assign an array of structures to a single cell."

"Instead I hav to access each structure through dot indexing"

You put the data into an structure yourself! How else would you expect to access it?

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Answer 1

Stephen23 2017-11-17

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https://ww2.mathworks.cn/matlabcentral/answers/367509-assign-an-array-of-structs-to-a-cell#answer_291732

编辑：Stephen23 2017-11-17

在 MATLAB Online 中打开

In your example code you need to change the indexing into the cell array from i to k:

carray{k} = results;

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Jerry Olup 2017-11-17

ugh, yes, thanks!

Jerry Olup 2017-11-17

And... tested, so it's fine to store any data in cell as expected. Simple indexing error. Thx again.

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