how i can save the value of two signals when they are equal

i want to save the value of these two signals when they have an equal value in each period

i wrote this code but it's not true

    a = zeros(1,14);
    if signal_1 == signal_2
       a(b) = signal_1
       b = b+1;
    end
     b=mod(b,14);

code needs to define the value of "b" and if i define that it cant continues to 14

[Raj]

Your 'if' condition logic will not serve the purpose. Depending on the first value of the signals, either the execution will not enter this condition or will enter and exit with only one match. Do you have the equations/workspace variables for signal_1 and signal_2?

[esmaeil keyvanloo]

no, signals produced by Simulink blocks

that's ok, I want to just when conditions are true the program save a new value on a(b)

Answer 1

[Walter Roberson]

N = 14;
a = zeros(1, N);
b = 1;
for K = 1 : length(signal_1)
    if signal_1(K) == signal_2(K)
        a(b) = signal_1(K);
        b = mod(b, N) + 1;
    end
end

I know that mod(b,N)+1 might look wrong, but it is correct. b = 1 is sent to 2, b = 2 is sent to 3, ... b = 13 is sent to 14, b = 14 then mod(b,14) is 0 and then you add 1 to that giving 1, so b = 14 is sent to 1.

[esmaeil keyvanloo]

thanks

your code is true, but this is a part of program and program should be run as long as conditions of if are fulfilled

[Walter Roberson]

I have to guess about meaningful outputs of this.

function a_copy = fcn(signal_1, signal_2)

N = 14;
persistent a b
if isempty(a) || isempty(b)
    a = zeros(1, N);
    b = 1;
end

if signal_1 == signal_2
    a(b) = signal_1;
    b = mod(b,N) + 1;
end

a_copy = a;

Answer 2

[esmaeil keyvanloo]

thanks, but still needs to define b

[Walter Roberson]

You could try adding

if isempty(b)
    b = 1;
end

Answer 3

[esmaeil keyvanloo]

grateful

unfortunately, that has the same error and need to define the value of b.

[Walter Roberson]

Perhaps you could use a global block to store a and b

Or make them signals that are given initial values and which feed back into the block. Just make sure that you have a unit delay block so you do not accidentally create an algebraic loop.