Why doesn't anything show up on my plot?

 clear all;
 clc;

 Fi=1000;

 Se= 50;
 Su= 450;

 C= 2/3;
 nf=[];

 for D=2:01:6;
    A= 0.25*pi*(D)^2;

    siga= ((C*3662.5+Fi)-(C*1000+1000))/2*A;
    sigm= ((C*3662.5+Fi)+(C*1000+1000))/2*A;

    sigi= sigm-siga;

    nf= (Se*(Su-sigi))/(siga*(Su+Se));
 end

 figure(1)
 D=2:6
 plot(D,nf)
 xlabel('D');
 ylabel('nf');

Answer 1

[Star Strider]

Define ‘D’ before the loop, and subscript ‘nf’ in the loop:

Fi=1000;

Se= 50;
Su= 450;

C= 2/3;
nf=[];

D=2:01:6;
for k = 1:numel(D)
    A= 0.25*pi*(D(k))^2;

      siga= ((C*3662.5+Fi)-(C*1000+1000))/2*A;
      sigm= ((C*3662.5+Fi)+(C*1000+1000))/2*A;

      sigi= sigm-siga;

      nf(k)= (Se*(Su-sigi))/(siga*(Su+Se));
  end

figure(1)
plot(D,nf)
xlabel('D');
ylabel('nf');

[Liam Swift]

Thank you.

[Star Strider]

As always, my pleasure.