what should I do. HELP function

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Bilal Ates
Bilal Ates 2020-6-26
评论： Bilal Ates 2020-6-28
[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

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采纳的回答

Gaurav Aggarwal
Gaurav Aggarwal 2020-6-26
编辑：Gaurav Aggarwal 2020-6-26
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.
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Gaurav Aggarwal
Gaurav Aggarwal 2020-6-28
Did it work for you? If so, it would be great if you accept the answer and close this query. Thanks.

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更多回答（1 个）

Steven Lord
Steven Lord 2020-6-26
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 个评论
Gaurav Aggarwal
Gaurav Aggarwal 2020-6-26
编辑：Gaurav Aggarwal 2020-6-26
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).
Bilal Ates
Bilal Ates 2020-6-28
Thank you all for your help

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