Matlab:将值添加到初始化的嵌套struct-cell中 [英] Matlab: adding value into initialized nested struct-cell

问题描述

我有这个结构

Data = struct('trials',{},'time',{},'theta_des',{},'vel_des',{},'trials_number',{},'sample_numbers',{});
Data(1).trials = cell(1,trials_number);
for i=1:trials_number
   Data.trials{i} = struct('theta',{},'pos_err',{},'vel',{},'vel_err',{},'f_uparm',{},'f_forearm',{},'m_uparm',{},'m_forearm',{},...
                           'current',{},'total_current',{},'control_output',{},'feedback',{},'feedforward',{},'kp',{});
end

但是当我想添加一个值

Data.trials{i}.theta = 27;

我收到此错误...

A dot name structure assignment is illegal when the structure is empty.  Use a subscript on the structure.

有什么解决方法的想法吗?

Any idea of how to solve it?

谢谢！

推荐答案

如果您查看

If you take a look at the documentation of struct, it says the following statement:

s = struct(field,value)使用指定的字段和值创建一个结构数组.

s = struct(field,value) creates a structure array with the specified field and values.

...

...

• 如果任何value输入是一个空单元格数组{}，则输出s是一个空(0×0)结构.

• If any value input is an empty cell array, {}, then output s is an empty (0-by-0) structure.

因为您的字段已初始化为{}，所以它们是空单元格数组，因此您将获得一个空结构，因此您无法访问该结构，因为它是空的.如果要初始化struct，请使用空括号代替[].换句话说，在您的for循环中，执行以下操作:

Because your fields are initialized to {}, these are empty cell arrays, you will get an empty structure, so you are not able to access into the structure as it's empty. If you want to initialize the struct, use the empty braces instead []. In other words, in your for loop, do this:

for i=1:trials_number
    Data.trials{i} = struct('theta',[],'pos_err',[],'vel',[],'vel_err',[],'f_uparm',[],'f_forearm' [],'m_uparm',[],'m_forearm',[],...
    'current',[],'total_current',[],'control_output',[],'feedback',[],'feedforward',[],'kp',[]);
end

这应该为您正确初始化结构，然后您可以相应地访问字段.因此，如果我想在单元格数组的第一个结构中初始化theta:

This should properly initialize the structure for you, and you can then access the fields accordingly. As such, if I wanted to initialize theta in the first structure within your cell array:

Data.trials{1}.theta = 27;

现在可以使用.您可以通过以下方式验证输出:

This will now work. You can verify the output by:

disp(Data.trials{1}.theta)

27

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