Euler Method in Fortran - HELP

[sayellow]

Euler Method in Fortran - HELP!

Using Euler method I want to calculate the equation below, deltat=0.3, 10 times.

Problem: When n=1, Yn1(1) is calculated right. But, in the following steps it should assume that Yn(2)=Yn1(1) and the program is assuming Yn(2)=0, as well as Yn(3)=0,...and so on
Please, can someone help me?

Program Exercise1
!
! This Program will solve the ODE bellow using Euler Method ...
!
! dy(t)
! ______ = 2y(t) + t^2 + t
! dt
!
! Declaration of Variables
!
Implicit none
!
!
Real:: deltat1

Integer:: ts1,n,time
Real:: Yn1(1:11),Yn(1:11),tn(1:11)

Yn(1)=1
do n=1,ts1
deltat=0.3
ts1=10

tn(n)=(deltat*(n-1))+tn(n)

Yn1(n+1)=Yn(n)+deltat*(2*Yn(n)+(tn(n)**2)+tn(n))
Yn(n)=Yn1(n+1)
write (*,*) Yn1(n)

enddo

n=n+1

End

 

[Integral]

first move the assignment statements for deltat and ts1 outside of your loop. You also have not initialize tn(0).

I am very uneasy with your incrementing your time variable in step with the Euler method iterations.

I think you should put the Euler loop inside of a time step loop. So you want to iterate a Euler loop at EACH time step.

You may want to look closely at the result of your time step calculation, is it producing what you want it to?

 

[quicknote]

Program Exercise1

I would suggest checking your code for any potential errors or mistakes. It seems like your program is not correctly updating the values of Yn and Yn1, which could be causing the issue you mentioned. You may also want to double check the initial conditions and make sure they are set correctly. Additionally, you can try debugging your code step by step to see where the error is occurring. If you are still having trouble, reaching out to a colleague or professor for assistance could also be helpful. Good luck!