Conversion to double from sym is not possible

Hi every body,

I am a beginner of matlab

this is my code

syms x;
A = [3*x , 0; 0.3*f , 0; 3 , 0; 1 , 0];

for a=1:2
    for b=1:2
        for c=1:2
            for d=1:2
                er=A(1,a);
                ei=A(2,b);
                ur=A(3,c);
                ui=A(4,d);

for d=1:3;

x=2:18;
e=er-1i*ei;
u=ur-1i*ui;

z=(abs((d*x)*(e*u)^0.5)));

plot(x,z)

end

              end
          end
      end
  end

when I come to plot, I get this message

Conversion to double from sym is not possible

help me please, have a nice life

[Andrei Bobrov]

what is it - 'f'

Answer 1

[petter]

 In the wide and broad world, never contact with each other, you gave me so useful help.

thank you for your timely answer and your discerning observation ('f' from my code, replaced on 'x')

To express my thanks, my function is named after "andrei bobrov".

I am a beginner in matlab. But I will try my best to help others in matlab just like you someday.

thank you again!

[Fangjun Jiang]

So why did you accept your own answer which is not really the solution to your problem? I suggest you delete this answer, add your acknowledgement as a comment and accept andrei's answer.

Answer 2

[Andrei Bobrov]

'f', from your code, replaced on 'x'

syms x; 
A = [3*x , 0; 0.3*x , 0; 3 , 0; 1 , 0];

for a=1:2 
    for b=1:2 
        for c=1:2 
            for d=1:2 
                er=A(1,a); 
                ei=A(2,b); 
                ur=A(3,c); 
                ui=A(4,d);
                for d1=1:3
                    x1= 2:18; 
                    e= er-1i*ei; 
                    u= ur-1i*ui;
                    z =  subs(abs(d1*x*e*u^0.5),x,x1) ;
                    figure;
                    plot(x1,z)
                end
            end
        end
    end
end

[Walter Roberson]

You probably need to plot(x1,double(z))