how to make if statement repeat only once ?

Question

tomer polsky 2018-5-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/401032-how-to-make-if-statement-repeat-only-once

评论： Mohamed Eldemerdash 2021-11-2

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

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Stephen23 2018-5-17

编辑：Stephen23 2018-5-17

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 2018-5-22

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

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Answer 1

Aakash Deep 2018-5-22

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在 MATLAB Online 中打开

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