replacement has length zero in R from a python code

Question

I was doing numerical method in R and Python I have applied leapfrog method in python and it worked perfectly but I want to do the slimier thing in R. Here you can see my code

Possibly I have tried doing u[2,2]=beta*(u[1,1]-2*u[2,1]+u[3,1]) this works, here I can see that the error is due to the bold statement means due to u[2,0] does not exist. But the same code worked in python, Please help to resolve the error while executing the loop

u[i, j - 1] evaluates to u[2, 0], or numeric(0). This is what produces the error. Is there any solution.

Answer 1

Keep in mind that R indexes are 1-based, while in Python they are 0-based. In your code, the first time through the for loop, u[i, j - 1] evaluates to u[2, 0], or numeric(0). This is what produces the error.