Some common sense question

Dear Lammps users,

Since I learn to use lammps, I have some common sense question. How can we calculate specific data by lammps data, is there any helpful code for calculating (For example, if I only want calculated the mid part) Or we need to output the data and then use the matlab to calculate it.?
Also, I am so confuse about the total energy, should the total energy be positive in lammps, or it could be negative?
If everyone could explain to me, it would help me a lot!

Kerwin

Dear Lammps users,
    Since I learn to use lammps, I have some common sense question. How
can we calculate specific data by lammps data, is there any helpful code
for calculating (For example, if I only want calculated the mid part) Or we
need to output the data and then use the matlab to calculate it.?

​these are not "common sense" questions, these are "confused" questions.
you are mixing a very specific query with very vague description: do you
mean by "calculate specific data"? what is a "mid part" (middle by what
measure?, part of what?)?​ output what "data"?

Also, I am so confuse about the total energy, should the total energy be
positive in lammps, or it could be negative?

​as has been explained many times, the absolute value of the potential
energy is arbitrary (see "pair_modify shift") and has no meaning; only
energy differences matter.

If everyone could explain to me, it would help me a lot!

​these seem to be very basic questions, most of which about rather
fundamental issues. this is a topic for a discussion with your
adviser/supervisor/tutor.

axel.​