how to integral2?

how can i integral a function which was written in matlab but there is wrong , i dont no where it is :

syms tau

syms y

f= @(y,tau)y*exp(-0.5.*y.^2/ tau)

expecty=integral2(f, -2,4,0,Inf,'auto')

Answer 1

[Birdman]

integral2 is defined for function handle, therefore you do not need symbolic variables:

 f= @(y,tau)y.*exp(-0.5.*y.^2./ tau)
 expecty=integral2(f, -2,4,0,Inf,'auto')

[elham kreem]

if i use it as a defined , the result is:

expecty =

   NaN

[Torsten]

The result is correct.

Did you expect something finite for the integral ?

[elham kreem]

do you mean that :

expecty = nan

is correct?

[Steven Lord]

When y = 0 and tau = 0, you're computing 0.*exp(0./0). 0./0 is NaN, exp(NaN) is NaN, and 0*NaN is NaN. Once NaN enters a calculation, it tends to propagate throughout that calculation.

[Torsten]

Neglecting numerical aspects like division by 0, your integral is +Inf.

Best wishes

Torsten.

[elham kreem]

gentelmen , thanks for your answers , but there is something wrong?

because the result is not convincing .

if i integrate the function with syms y and tau , are the code right and the result?

syms tau

syms y

fun = @(y,tau) (1/tau) * y * exp((-0.5*y^2 / tau)

f1 = int(fun , y ,tau )

is this mean double integral , for y and tau?

the result is

exp(-y^2/(2*tau)) - exp(-tau/2)

 is the result convincing?