Error:Field and value input arguments must come in pairs

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

Answer 1

[Walter Roberson]

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)

Answer 2

[NALLARASU KRISH]

When you create or modify struct in Matlab, you may ensure that the number of fields be in even number.