what should I do. HELP function
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Bilal Ates
le 26 Juin 2020
Commenté : Bilal Ates
le 28 Juin 2020
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/322357/image.png)
[y, z]=rungeKutta(2,4,0,1,10000)
function dydx=f(x,y,z)
dydx=-2*y + 4*exp(-x) + exp(-1000*(z^2));
end
function dzdx=g(y,z)
dzdx=-y*(z^2)/3;
end
function [y,z]=rungeKutta(y0,z0,x0,xn,n)
h=(xn-x0)/n;
x=x0;
y=y0;
x=x0;
for i=1:n
k0=h*f(x,y,z);
l0=h*g(y,z);
k1=h*f(x+h/2, y+ k0/2, z+ lo/2);
l1=h*g(y+ k0/2, z+ lo/2);
k2=h*f(x+h/2, y+ k1/2, z+ l1/2);
l1=h*g(y+ k1/2, z+ l1/2);
k3=h*f(x+h, y+ k2, z+ l2);
l3=h*g(y+ k2, z+ l2);
y=y + (k0+2*k1+2*k2+k3)/6;
z=z + (l0+2*l1+2*l2+l3)/6;
end
end
Réponse acceptée
Gaurav Aggarwal
le 26 Juin 2020
Modifié(e) : Gaurav Aggarwal
le 26 Juin 2020
Hi Bilal,
Your code seems to have many undefined variables, like z in line 15, lo in line17, l2 in line 22.
See if the following code works for you and gives the output according to your expectations.
[y, z]=rungeKutta(2,4,0,1,10000)
function dydx=f(x,y,z)
dydx=-2*y + 4*exp(-x) + exp(-1000*(z^2));
end
function dzdx=g(y,z)
dzdx=-y*(z^2)/3;
end
function [y,z]=rungeKutta(y0,z0,x0,xn,n)
h=(xn-x0)/n;
x=x0;
y=y0;
x=x0;
z=z0; %% z added
for i=1:n
k0=h*f(x,y,z);
l0=h*g(y,z);
k1=h*f(x+h/2, y+ k0/2, z+ l0/2); %% lo -> l0
l1=h*g(y+ k0/2, z+ l0/2);
k2=h*f(x+h/2, y+ k1/2, z+ l1/2);
l2=h*g(y+ k1/2, z+ l1/2); %% variable name l1 -> l2
k3=h*f(x+h, y+ k2, z+ l2);
l3=h*g(y+ k2, z+ l2);
y=y + (k0+2*k1+2*k2+k3)/6;
z=z + (l0+2*l1+2*l2+l3)/6;
end
end
Hope it helps. Thanks.
3 commentaires
Gaurav Aggarwal
le 28 Juin 2020
Did it work for you? If so, it would be great if you accept the answer and close this query. Thanks.
Plus de réponses (1)
Steven Lord
le 26 Juin 2020
As stated on this documentation page "Script files cannot have the same name as a function in the file." Either rename your script file to something other than rungeKutta.m or rename the function you define on line 9 of rungeKutta.m to something other than rungeKutta.
2 commentaires
Gaurav Aggarwal
le 26 Juin 2020
Modifié(e) : Gaurav Aggarwal
le 26 Juin 2020
After defining some variables, the script worked for me. The script's name and the function name were same in my case. As per my understanding, it doesn't matter as long as the function call is within the file scope, which seems to be the case with Bilal's (acc. to the code he provided).
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