通过字段名称和一些非顺序索引选择结构元素 [英] Pick a struct element by field name and some non-sequential index

问题描述

我的意思是使用结构来保存表格":

I mean to use a struct to hold a "table":

% Sample data
% idx  idxstr  var1  var2  var3
%   1    i01    3.5  21.0   5
%  12    i12    6.5   1.0   3

第一行包含字段名称.假设我创建了一个结构

The first row contains the field names. Assume I created a struct

ds2 = struct( ...
    'idx', { 1, 12 }, ...
    'idxstr', { 'i01', 'i12' }, ...
    'var1', { 3.5, 6.5 }, ...
    'var2', { 21, 1 }, ...
    'var3', { 5, 3 } ...
);

如何检索字段 var2 的值，对应于 idxstr 的行等于 'i01'?

How can I retrieve the value for field var2, for the row corresponding to idxstr equal to 'i01'?

注意事项:

1. 我无法确保 idxstr 元素的长度始终为 3.
2. 理想情况下，我会有一种方法也适用于包含字符串或任何其他类型变量的列 var2.

1. I cannot ensure the length of idxstr elements will always be 3.
2. Ideally, I would have a method that also works for columns var2 containing strings, or any other type of variable.

PS:我认为 https://stackoverflow.com/a/35976320/2707864 可以提供帮助.

PS: I think https://stackoverflow.com/a/35976320/2707864 can help.

推荐答案

假设 idxstr 可以超过 3 个字符(有一个较短的版本，它总是 3 个字符)，就是这样我想出了(在 MATLAB 上测试):

Assuming that idxstr can be more than 3 characters (there is a shorter version of its always 3 chars), this is the thing I came up with (tested on MATLAB):

logical_index=~cellfun(@isempty,strfind({ds2(:).idxstr},'i01'))

您可以通过以下方式访问变量:

you can access the variables as:

ds2(~cellfun(@isempty,strfind({ds2(:).idxstr},'i01'))).var2;
% using above variable
ds2(logical_index).var2;

现在你可以理解为什么 MATLAB 会引入表格了，呵呵.

You can understand now why MATLAB introduced tables hehe.

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