Matlab的arrayfun用于类对象的统一输出 [英] Matlab's arrayfun for uniform output of class objects

问题描述

我需要使用arrayfun建立类 ID 的对象数组：

I need to build an array of objects of class ID using arrayfun:

% ID.m
classdef ID < handle
    properties
        id
    end
    methods
        function obj = ID(id)
            obj.id = id;
        end
    end
end

但遇到错误：

>> ids = 1:5;
>> s = arrayfun(@(id) ID(id), ids) 
??? Error using ==> arrayfun
ID output type is not currently implemented.

我可以循环构建：

s = [];
for k = 1 : length(ids)
    s = cat(1, s, ID(ids(k)));
end

但是arrayfun的用法有什么问题？

but what is wrong with this usage of arrayfun?

编辑（问题的澄清）：问题不是如何解决问题（有几个解决方案），但为什么简单的语法 s = arrayfun（@ id）ID（id），ids）; 不工作。谢谢。

Edit (clarification of the question): The question is not how to workaround the problem (there are several solutions), but why the simple syntax s = arrayfun(@(id) ID(id), ids); doesn't work. Thanks.

推荐答案

您要求 arrayfun t。

arrayfun 的输出必须是：

The output from arrayfun must be:

标量值数字，逻辑，字符或结构）或单元
数组。

scalar values (numeric, logical, character, or structure) or cell arrays.

对象不计为任何标量类型，这就是为什么解决方法都涉及使用单元格阵列作为输出。有一件事要尝试使用 cell2mat 将输出转换为所需的形式;它可以在一行中完成。 （我没有测试它。）

Objects don't count as any of the scalar types, which is why the "workarounds" all involve using a cell array as the output. One thing to try is using cell2mat to convert the output to your desired form; it can be done in one line. (I haven't tested it though.)

s = cell2mat(arrayfun(@(id) ID(id), ids,'UniformOutput',false));

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