how to define an integral function

2018 9 6
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更新时间：2023 4 1
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0 个投票

I want to define a function in the integral form
f(x)=integral(g(z), z=0, z=x)
as an example:
for which I wrote:
fun = @(z) z^2+3*z-1;
x=linspace(0,1,100);
y = integral(fun,0,@(x) x)
plot(x,y)
But Matlab returned the following error:
Error using integral (line 85)
A and B must be floating-point scalars.
Error in IntegralFunction (line 8)
y = integral(fun,0,@(x) x)
Is it possible at all to do this in Matlab?

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 采纳的回答

Torsten
Torsten 2018-9-6

2 个投票

fun=@(z)z.^2+3*z-1;
F=@(x)integral(fun,0,x);
F(10)

5 个评论
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Saeid
Saeid 2018-9-6
Danke, Torsten!
Saeid
Saeid 2018-9-7
编辑：Saeid 2018-9-7
Hi again Torsten! Actually, my aim to define a function like this was for the final result (in this case F(x)=x^3/3+3*x^2/2-x) to be a coefficient in a differential equation. Something like: y"+F(x).y'=y"+(x^3/3+3*x^2/2-x)*y'=0 Do you know if that is possible in Matlab?
Torsten
Torsten 2018-9-7
Yes, it's possible just the way I showed you above. What exactly is the problem when you want to use it in your context ?
Saeid
Saeid 2018-9-7
I tried the following format but it didn't work:
tspan = [0 5];
y0 = 0;
[t,y] = ode45(@(t,y) DYDT(t,y) , tspan, y0);
plot(t,y,'-o')
function dydt=DYDT(t,y)
fun=@(z)z.^2+3*z-1;
dydt=@(y)integral(fun,0,y)
end
Hey, I am also stuck with the same proble, did you find the solution? Can you please help me out with this?

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