function [E,r_x] =rs_channel(t_x,N,Position,ERROR)
%本函數實現指定錯誤下的信道傳輸過程
%t_x為發送端編碼器輸出，N為出錯個數，Position為指定的錯誤位置，ERROR為指定的錯誤數值
temp = Position;
temp2=ERROR;
Position = zeros(1,length(t_x));
for i= 1:length(temp)
    j = temp(i)+1;
    Position(j) = 1;
end
m = 1;
temp2 = ERROR;
ERROR = zeros(1,length(Position));
for j=1:length(Position)
    if Position(j)~=0
          ERROR(j) = temp2(m);
          m=m+1;
    end
end
    if sum(Position)~=N|length(Position)~=length(t_x)|length(ERROR)~=length(t_x)
     E = zeros(1,length(t_x));
     r_x=zeros(1,length(t_x));
    else
      for i=1:length(t_x)
         r_x(i) = rs_symboladd(ERROR(i),t_x(i));
      end
      E = ERROR;
    end