Why is 0 not valid in mean fucntion?

Hello,

I have this function:

function [coin, I,evAlice,evBob] = CH_(sigma_x,sigma_z)
ev1_of_alice = sigma_x;
    ev2_of_alice = sigma_z;
    ev1_of_bob = sigma_x+sigma_z;
    ev2_of_bob = sigma_x-sigma_z;
S = + mean(coin(ev1_of_alice,ev1_of_bob)) ...
        - mean(coin(ev1_of_alice,ev2_of_bob)) ...
        + mean(coin(ev2_of_alice,ev1_of_bob)) ...
        + mean(coin(ev2_of_alice,ev2_of_bob));
    if ~isnan(S)
        fprintf("S = " + S + "\n");
        if abs(S) > 2
            fprintf("V! (|S|>2)\n")
        end
    else
        fprintf("Not enough data to determine S\n")

But when coin has "0" value like that coin (1,0) or (0,1) I have this error:

  Index in position 1(2) is invalid. Array indices must be positive integers or logical values.

why I am getting that how can I fixed it?

[the cyclist]

Can you give an example of calling this function, that gives that error?

[the cyclist]

Oh, also, this is confusing, because you output coin like a variable, but you also are calling it as a function (it seems). I think you might have a more fundamental problem with the code.

[Devineni Aslesha]

I am assuming that the coin is other nested function defined in CH_. function. Using the same name for variable and nested function is not supported in nested functions. Refer this link for more information.

But it seems that the coin is considered as an array from the above error. It would be helpful if you provide the entire code and give an example of calling CH_ function to replicate the error.