Get data from multi-level struct using strings

4 次查看（过去 30 天）

Niklas Nylén 2017-10-25

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/363108-get-data-from-multi-level-struct-using-strings

评论： Niklas Nylén 2017-11-6

I need to read data into matlab where a text file specifies the structure and index of the data and another file contains the data itself.

Currently the implementation is done using an eval statement, e.g.

eval(['data.' dataName '=value;'])

I would like to use parfor instead since there are a many large files to process but parfor doesn't allow eval. I tried fixing it by replacing the eval statement with:

data.(dataName) = value;

The issue I'm running into is that dataName specifies multiple levels of a struct, e.g. dataName = 'a.b.c', which gives me an error.

Is there any way to make this work?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Stephen23 2017-10-25

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/363108-get-data-from-multi-level-struct-using-strings#answer_287607

编辑：Stephen23 2017-10-25

在 MATLAB Online 中打开

You can use setfield and getfield with nested fields. Unfortunately the help description is quite vague on how to do this, but all you need to do is supply all the fieldnames individually:

>> val  = 1;
>> name = 'a.b.c';
>> C = regexp(name,'\.','split');
>> data = setfield(struct(),C{:},val);
>> data.a.b.c
ans =  1

This is much more reliable than using eval, although it is possible that setting fields like this is also not permitted within a parfor loop, but it is worth a try.

7 个评论
显示 5更早的评论隐藏 5更早的评论

Niklas Nylén 2017-10-26

Great! I tried to do this way before but I didn't know about the num2cell function. Thank you.

Niklas Nylén 2017-11-6

在 MATLAB Online 中打开

So, the final version, which also supports assigning arrays as value:

name = 'aaa.bb(3).cc.de(7)';
data = struct();
val = [5 3 2];
C = regexp(name,'[\.()]+','split');
C = C(~cellfun(@isempty, C));
V = str2double(C);
idx = isfinite(V);
C(idx) = num2cell(num2cell(V(idx)));
if idx(end)
    C{end} = [C{end} ':'];
end
data = setfield(data, C{:}, val);