how to make if statement repeat only once ?

hello I am currently doing a project with matlab and simulink.

In my project I am taking current samples from matlab function and making is statment for a switch .

the problem is that my statment is working all the time , meaning that for exmaple my switch is on "1" and it is switching to "0" I want it to stay like this and not creak the statement again how is it possible ?

   function [final_resolt]=relay_condition(u)
  format long;

         i_diff_1=u(1)-u(4);
         i_diff_2=u(2)-u(5);
         i_diff_3=u(3)-u(6);

         ind_1=u(1)*u(4);
         ind_2=u(2)*u(5);
         ind_3=u(3)*u(6);

         I_diff_1=0;
         I_diff_2=0;
         I_diff_3=0;

         IND_1=1;
         IND_2=1;
         IND_3=1;

         m=20;
         I_min=1000;

         for i=1:1:m

         I_diff_1=(I_diff_1+i_diff_1^2);
         I_diff_2=(I_diff_2+i_diff_2^2);
         I_diff_3=(I_diff_3+i_diff_3^2);

         IND_1=(IND_1*ind_1)/1;
         IND_2=(IND_2*ind_2)/1;
         IND_3=(IND_3*ind_3)/1;

         end

         I_diff_1=(I_diff_1/m)^0.5;
         I_diff_2=(I_diff_2/m)^0.5;
         I_diff_3=(I_diff_3/m)^0.5;

         IND_1=IND_1/m;
         IND_2=IND_2/m;
         IND_3=IND_3/m;

                      if (I_diff_3>I_min )

                       final_resolt=0; 
                      else

                       final_resolt=1;
                      end

end

[Geoff Hayes]

tomer - please clarify what you are attempting to do as it isn't clear (to me) what the switch is. Is the problem with the if block? Do you only want to evaluate it once?

[Stephen23]

tomer polsky's "Answer" moved here:

Ye this exactly what I want to do . u are currents from simulink and the final resolt is the switch . I want it to change only when time , when it changes to zero stay in this condition.

[Guillaume]

Since the if statement is outside of any loop, it will execute only once. Hence it's not clear what the problem is.

Answer 1

[Aakash Deep]

Hey,

From your question, I understand that you have a if condition inside a loop which you need to execute only once for a particular condition. In order to do this you can use a flag variable. Let's see this with an example, let's suppose you have an array with values 0 and 1. You have to subtract value x only on the first zero in the array.

arr = [1,1,1,0,0,1,0,0]; 

flag = 0; 

for i = 1:len(arr) 

     if( flag == 0 && arr(i) == 0 ) 

        arr(i)= arr(i) – x; 

        flag = 1;               % important part 

     end 

     % loop_continue 

end

Hope this helps

Thanks,

Aakash Deep

[Mohamed Eldemerdash]

Thanks Akash this worked for me.