Hi every one, can you help me to draw graph Frequency and transmissibility (or Amplitude) from code:

function main
d1=1;
v=10;
t_end=100*0.5*d1/v;
t=0:0.01:t_end;
y0=[0;0;0;0];
[t,y]=ode45(@daodong,t,y0);
hold on;grid on;
plot(t,y(:,1));
xlabel('Thoi gian (s)')
ylabel('Bien Do dao dong (m)')
title('DAO DONG CUA HANH KHACH')

Fs=10;
freq1 = 0:Fs/length(x1):Fs/2;
hold on;grid on;
plot(freq,abs(xdft),'g')
plot(freq1,abs(xdft1),'r')
xlabel('Hz')
ylabel('Amplitude')
legend('NEM HOI')
end
function yp = daodong(t,y)
c=10;
vt=10;
k1=84.24;
m1=5.265;
I1=0.2322;
a=0.21;
yp = zeros(4,1);
yp(1) = y(2);
yp(2) = ((-(c*(y(2)-0.05*2*pi*vt*(sin(4*pi*vt*t))-(a*y(4)/2))+k1*(y(1)-(0.05*(sin(2*pi*vt*t))^2)-(a*y(3)/2))))/m1);
yp(3) = y(4);
yp(4) = ((-(a*c*(y(2)-0.05*2*pi*vt*(sin(4*pi*vt*t))-(a*y(4)/2))+a*k1*(y(1)-(0.05*(sin(2*pi*vt*t))^2)-(a*y(3)/2))))/(2*I1));
end

Thank you very much.

[Walter Roberson]

In your line

freq1 = 0:Fs/length(x1):Fs/2;

x1 is not defined.

In your line

plot(freq,abs(xdft),'g')

xdft is not defined.

[Johnny Vendetta]

i'm sorry, my code:

function main
d1=1;
v=10;
t_end=100*0.5*d1/v;
t=0:0.01:t_end;
y0=[0;0;0;0];
[t,y]=ode45(@daodong,t,y0);
hold on;grid on;
plot(t,y(:,1));
xlabel('Thoi gian (s)')
ylabel('Bien Do dao dong (m)')
title('DAO DONG CUA HANH KHACH')
end
function yp = daodong(t,y)
c=10;
vt=10;
k1=84.24;
m1=5.265;
I1=0.2322;
a=0.21;
yp = zeros(4,1);
yp(1) = y(2);
yp(2) = ((-(c*(y(2)-0.05*2*pi*vt*(sin(4*pi*vt*t))-(a*y(4)/2))+k1*(y(1)-(0.05*(sin(2*pi*vt*t))^2)-(a*y(3)/2))))/m1);
yp(3) = y(4);
yp(4) = ((-(a*c*(y(2)-0.05*2*pi*vt*(sin(4*pi*vt*t))-(a*y(4)/2))+a*k1*(y(1)-(0.05*(sin(2*pi*vt*t))^2)-(a*y(3)/2))))/(2*I1));
end

Can you help me to draw graph Frequency and transmissibility (or Amplitude).