ODE function in a loop
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I have a function of x and t, and am creating a loop to find the average x/t for every U. I have successfully used this method before, however my x values are zero every time.
My function is:
function dx=myfunction(t,x,U)
de=24.35;
dd=294.5.*10^(-9);
hbar=6.5.*10^(-16);%
lambda=20*d;
k=(2.*pi)/(lambda);
v=2.5.*10^(-3);
dx=zeros(3,1);
dx(1)=((de)/(2.*hbar.*v.*k)).*sin(x(2));
dx(2)=(dd.*U)./(hbar.*2*v).*(cos(((pi.*x(1))/10)-(t)));
end
In the loop:
dU=1;
U=0:dU:200;%
tspan=[1 30];
vx=zeros(size(U));
for j=1:length(U)
[t,x]=ode45(@(t,x) myfunction(t,x,U(j)),tspan,[0 0 0]);
vx(j)=(sum((x(:,1))./(t))./(length(t));
end
Any ideas as to why the changing of U gives x a value of 0 would be useful.
Thanks in advance.
回答（1 个）
Jan
2017-3-3
The code will not run at all, because the number of parenthesis in
vx(j) = (sum((x(:,1))./(t))./(length(t));
is wrong. I guess you want:
vx(j) = sum(x(:,1) ./ t) ./ length(t);
It is useful to use additional parenthesis, if it improves the readability of the code, but here this was an overdoing.
If this is fixed, runnign your code fails in the line:
lambda=20*d;
due to an undefined variable "d".
Finally all I can suggest to use the debugger to examine, what's going on. Set a breakpoint in your code and step through the program line by line. This helps to understand, where which values are defined. Please post the running code afterwards, if you still have problems.
2 个评论
Physics
2017-3-3
Walter Roberson
2017-3-4
If you are still having difficulty, please post corrected code.
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2017-3-4
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