Help me plot my first function, please

Hello. I'm a complete beginner when it comes to MATLAB and couldn't find a question that helped me. (Probably because I don't know the right terms to search). Sorry.

Why can't I plot this function? It worked on a smaller scale in a test file i made.

I get error: "Undefined function or variable 'r'." But I defined it in the function.

tx = 40 * 10^-10;
ex = 3.45*10^-13;
on = 180;
Vn = 0.25;
WLn = 0.12/1.4;

B = (on * (ex/tx)*WLn)

fplot(r)

function r = In(Vsn)
r = B*(1.2 - Vn - (Vsn/2))*Vsn
end

Answer 1

[Walter Roberson]

You could use:

tx = 40 * 10^-10;
ex = 3.45*10^-13;
on = 180;
Vn = 0.25;
WLn = 0.12/1.4;

B = (on * (ex/tx)*WLn);

r = @(Vsn) B*(1.2 - Vn - (Vsn/2)).*Vsn;

fplot(r)

The above can be used as a script file.

Any variable that you define in a function only exists while the function is executing.

You were not executing the function named In at all.

Also, your function used values that were defined in the script and not passed into the function.

You could also have used

function my_first_plot
  tx = 40 * 10^-10;
  ex = 3.45*10^-13;
  on = 180;
  Vn = 0.25;
  WLn = 0.12/1.4;

    fplot(@In)

    function r = In(Vsn)
      r = B*(1.2 - Vn - (Vsn/2))*Vsn
    end
  end

This is a more advanced program that shares variables with a nested function.

[Magnarok]

Is Vsn now the x-axis?