# Can you help me please !

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Johnny Vendetta on 3 Sep 2019
Commented: Johnny Vendetta on 7 Sep 2019
I run code Matlab:
function yp=khidonghoc(t,y)
m = 10;
cd = 0.2;
g = 9.81;
w = m*g;
tspan=[0 5];
y0=[0;100;0;10];
yp = zeros(4,1);
yp(1)= y(2);
yp(2) = ((-cd/m)*y(2)*(y(2)^2+y(4)^2)^(0.5));
yp(3) = y(4);
yp(4) = ((-w/m)-(cd/m)*y(4)*(y(2)^2+y(4)^2)^(0.5));
[t,y]=ode45('khidonghoc',tspan,y0);
plot(t,y(:,1),y(:,3))
hold on;grid on;
xlabel('X-Displacement')
ylabel('Y-Displacement')
title('X vs Y Displacement')
end
Matlab error: "Not enough input arguments.
Error in khidonghoc (line 9)
yp(1)= y(2);"
Thanks you very much.

Pass in some arguments! How did you call the function? It expects two input arguments so if you don't pass them in it will give you that error.
Johnny Vendetta on 7 Sep 2019

Torsten on 3 Sep 2019
function main
tspan=[0 5];
y0=[0;100;0;10];
[t,y]=ode45(@khidonghoc,tspan,y0);
plot(t,y(:,1),t,y(:,3))
hold on;grid on;
xlabel('X-Displacement')
ylabel('Y-Displacement')
title('X vs Y Displacement')
end
function yp=khidonghoc(t,y)
m = 10;
cd = 0.2;
g = 9.81;
w = m*g;
yp = zeros(4,1);
yp(1)= y(2);
yp(2) = ((-cd/m)*y(2)*(y(2)^2+y(4)^2)^(0.5));
yp(3) = y(4);
yp(4) = ((-w/m)-(cd/m)*y(4)*(y(2)^2+y(4)^2)^(0.5));
end

#### 1 Comment

Johnny Vendetta on 3 Sep 2019
Thank you so much, Torsten.