Error:Field and value input arguments must come in pairs

Question

Nagesh A P 2018-7-11

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/409757-error-field-and-value-input-arguments-must-come-in-pairs

回答： NALLARASU KRISH 2022-12-23

I have a code with a structure array a which is initialized as follows

 if true
    a=struct([]); 
    for i=1:(v_max+5)/5 
      a(i).v_low=0;
      a(i).v_up=0;
      a(i).t_cat=0;
      a(i).idlecat_p=0;
      %Assign value to each field in the structure array.
    end
 end

Now I'm trying to make another structure array b with same fields as of a

if true
  f=fieldnames(a);
  b=struct(f{:},0);
end

Till now I didn't have the field idlecat_p but soon as I added that to a, I'm getting the following error:

if true
Error using struct
Field and value input arguments must come in pairs.
Error in Code (line 373)
b=struct(f{:},0);                                                  
end

It's like whenever I'm adding a new field to a, the above error is coming at the same line

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Answer 1

Walter Roberson 2018-7-11

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/409757-error-field-and-value-input-arguments-must-come-in-pairs#answer_328341

在 MATLAB Online 中打开

Remember that when f is a cell array that struct(f{:},0) is the same as writing

struct(f{1}, f{2}, f{3}, f{4}, ... f{end}, 0)

which tells struct to use f{1} as a fieldname and give it the value f{2}, and to use f{3} as a fieldname and to give it the value f{4}, and so on, eventually taking the last field name and giving it a value of 0.

This can only work if you had an odd number of field names, so that the odd ones all get paired up with the following even one, except that the last odd one gets paired up with the 0 you provided.

cell2struct( repmat({0}, 1, length(f)), f, 2)