creating structures in nested for loop

I want to create a struct inside a nested for loop i am getting error, can someone explain or guide me a---> Integer b---> double c----> double value

for a=1:5
for b=0:0.1:1
    %x=num2cell(b);
field1='hey'; value1=a;
field2='bey'; value2=num2cell(b);
field3='cey'; value3=num2cell(c);
%ish=zeros(50,5);
ish(a,b)=struct(field1,(value1),field2,(value2),field3,(value3));
end
end

I tried to reallocate memory before running still i do not get the desired result

Error is : Subscript indices must either be real positive integers or logical s.

Answer 1

[Guillaume]

The problem has nothing to do with structures. You're using an non-integer b as a subscript into a matrix (of structures in this case but the same would be true with a matrix of number). This is not allowed in matlab. As the error message says: "Subscript indices must either be real positive integers or logical"

Note that if all you want to is create a structure a numel(a) x numel(b) structure with a, b, and the scalar c, then:

a = 1:5;
b = 0:0.1:1;
c = pi; %or whatever value you want
[aa, bb, cc] = ndgrid(a, b, c);
ish = struct('hey', num2cell(aa), 'bey', num2cell(bb), 'cey', num2cell(c))

Note that in your original code, since you're putting scalars into each field, the conversion to cell with num2cell is completely unnecessary.

[Yash]

I tried it but only the last value in the loop is getting saved i want to create a table that runs through nested loop and create and stores the value of a,b and c. can you please help

[Guillaume]

"I tried it". What does it refer to? The code I've shown does not have a loop (since it's not needed) and creates a 5x11 structure array.

" i want to create a table" You want a table or a structure? Note that you can't have an array of tables.

[Yash]

Is it possible to create a table using structure of array?? Or is it better to create a table inside nested for loop using http://nl.mathworks.com/help/matlab/ref/table.html

[Guillaume]

You can create a table from a structure, a cell array, a matrix or directly and fill it up in a loop.

I've no idea what you're trying to do anymore as this seems completely unrelated to your original example. Note that tables are not really practical for 3D data as in your example (2D matrix + fields).

Answer 2

[Thorsten]

You use b as index into a matrix

 ish(a,b)

with b=0:0.1:1. This does not work, indices have to be 1, 2, 3,... or logical, i.e. false or true (logical 0 or logical 1).

One way to do it:

% fields can be defined outside loop when they are always the same
field1='hey'; 
field2='bey'; 
field3='cry';

b = 0:0.1:1;
c = 23; % you forgot to define c

for a = 1:5
  for i = 1:numel(b) % generate index into b
    ist(a, i) = struct(field1,a,field2,b(i),field3,c);
  end
end

[Yash]

Is there any method to use b in ish(a,b) ?

[Guillaume]

For matrices, Subscript indices must either be real positive integers or logical is an absolute rule in matlab.