Error when using the function ODE45

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Stephanie Velasco
Stephanie Velasco 2017-2-24
编辑： Walter Roberson 2017-2-25
I have written to the following function to solve a differential equation using ODE 45, but i always seem to come across an error saying the "Inputs must be floats, namely single or double.". I am trying to solve for dt/dx,t(x)= 1/(a*x^(0.6)-b*x)), to find the time. but i get an error every time. since I have x in the equation idk what I'm doing wrong.
script
x_interval=[0.5 10];
t0 = [0];
[x,t] = Ode45(diff_,x_interval,t0);
function dt/dx = diff_(x,t)
a = 10;
b=0.5;
syms x;
t = (1/(a*x^(0.6)-b*x));
dt_dx =t;
end
  2 个评论
John D'Errico
John D'Errico 2017-2-24
How is this question significantly different from the last time you asked it, asking for help on solving the same question? Please stop making multiple postings for the very same problem.
Stephanie Velasco
Stephanie Velasco 2017-2-25
I wasn't sure if this one was clear enough, Im sorry about that. Have a blessed day

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采纳的回答

John Chilleri
John Chilleri 2017-2-25
Hello,
You just need to change a few things:
Script - missing an @ symbol.
x_interval=[0.5 10];
t0 = 0;
[x,t] = ode45(@diff_,x_interval,t0);
Function - don't use sym and you have a / in the name.
function dt_dx = diff_(x,t)
dt_dx = (1/(10*x^(0.6)-.5*x));
end
I simplified your function, but you can leave it as,
function dt_dx = diff_(x,t)
a = 10;
b=0.5;
t = (1/(a*x^(0.6)-b*x));
dt_dx =t;
end
Hope this helps!

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