Input argument for ode45 function type error

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Aleem Andrew on 7 Nov 2021
Commented: Star Strider on 7 Nov 2021
I am trying to modify the following code.
tspan = [0 10];
x0 = 0;
[t,x] = ode45(@(t,x) (-4.76e+1*x^2 + 5.69e-9*x + 7.98e-2)/(1.67e+4*x + 1.12), tspan, x0);
plot(t,x,'b')
xlim([0 0.001])
The input argument to the ode45 function is directly typed in. If instead you write it as
tspan = [0 10];
x0 = 0;
f = (-4.76e+1*x^2 + 5.69e-9*x + 7.98e-2)/(1.67e+4*x + 1.12);
[t,x] = ode45(@(t,x) f, tspan, x0);
plot(t,x,'b')
xlim([0 0.001])
then there is an error, even though the type of the argument is the same. Can anyone explain how the argument can be input as a variable that stores the expression?

Star Strider on 7 Nov 2021
Yes.
Create it as an anonymous function at the outset —
tspan = [0 10];
x0 = 0;
f = @(t,x) (-4.76e+1*x^2 + 5.69e-9*x + 7.98e-2)/(1.67e+4*x + 1.12);
[t,x] = ode45(f, tspan, x0);
figure
plot(t,x,'b')
grid
xlim([0 0.001]) .
Star Strider on 7 Nov 2021
As always, my pleasure!
.