## 60 Reputation

8 years, 138 days

## MaplePrimes Activity

### These are questions asked by zhuxian

MaplePrimes

Sorry, I comment not for answering question.

I want to ask a question, but I can't enter any 'Tags', but they need at least one tag.

There is not any text box where I can enter a tag.

Who can help me?

thanks!

## How to shift subscript?...

Maple 2017

Hi,

I asked a question before, how to shift subscript of u(i,j):

P: u[i,j] -->  u[i+1,j]

https://www.mapleprimes.com/questions/223136-How-To-Define-An-Operator

P: u[i,j]^2 v[i,j]+u[i-1,j]  -->  u[i+1,j]^2 v[i,j]+u[i,j]

thanks.

## discrete variational computation...

Maple 2017

Hi, I need to calculate some discrete variational problems, but it's a hard work just by hand.

Is there any toolboxes about the discrete variational computation? Or how to design a program to do that?

In particular, I need to realize the functions:

1. the linearized operator and the adjoint operator of some expressions.

For example:

the linearized operator of u(n,m+1)u(n+1,m) is u(n+1,m)Tm+u(n,m+1)Tn

(The latter is just the discrete Euler operator.)

Tm, Tn is the shift operator, T^(-1) is the inverse operator of T.

2. discrete Euler-Lagrange equation.

Thanks.

## How to define an operator?...

Hi,

I want to define an operator P, which can shift the first subscript of u(i,j)

P: u(i,j)->u(i+1,j)

and similarly,

Q: u(i,j)->u(i,j+1)

Thanks.

Maple

 (1)

 (2)

 (3)

 (4)

Just as the result above, I can't interpret why the last term of the formula (4) is (2)_xx.

Is ther a bug, or just because I made a mistake somewhere???

Thanks!