how to do smoothen this graph

this is my coding.

f=5000;
C=[2.000 1.000 0.665 0.500 0.400];
Xc=[15 30 48 58 76];

%% a
data=C*10^-6*f
eq=1./data

%% b
figure
subplot(4,4,[(1,2);(5,6)])
p=polyfit(C,Xc,2)
f=polyval(p,C); 
f2=p(1)*C.^2+p(2)*C+p(3)
plot(C,Xc,'o',C,f,'--') 
axis([0 2 10 80]);
legend('Experiment Data','Polynomial Fitting', 'Location','northeast')
xlabel('C(\muF)')
ylabel('XC(\Omega)')

Answer 1

[Walter Roberson]

f=5000;
C=[2.000 1.000 0.665 0.500 0.400];
Xc=[15 30 48 58 76];

%% a
data=C*10^-6*f

data = 1×5

0.0100 0.0050 0.0033 0.0025 0.0020

eq=1./data

eq = 1×5

100.0000 200.0000 300.7519 400.0000 500.0000

%% b
figure
subplot(4,4,[1,2;5,6])
p=polyfit(C,Xc,2)

p = 1×3

37.4192 -125.1775 115.8899

Cinterp = linspace(min(C),max(C));
f = polyval(p, Cinterp); 
f2=p(1)*C.^2+p(2)*C+p(3)

f2 = 1×5

15.2118 28.1316 49.1946 62.6560 71.8060

plot(C, Xc, 'o', Cinterp, f, '--') 
axis([0 2 10 80]);
legend('Experiment Data','Polynomial Fitting', 'Location','northeast')
xlabel('C(\muF)')
ylabel('XC(\Omega)')