How to assign table parameters to use it many times

Question

I'm using two nested Table to generate data which depend on two parameters, let's say it is temperature and pressure, many times in my code. When I change the temp and pressure values in calculations, I have to manually change it in all of the nested ``Table```. Here's simple example:

Table[Table[temp + press, {temp, 200, 500, 100}], {press, 1, 4}]
(* Out: {{201, 301, 401, 501}, {202, 302, 402, 502}, {203, 303, 403, 
  503}, {204, 304, 404, 504}} *)

Is there any way to define firstly parts of tables {temp, 200, 500, 100} and {press, 1, 4} and just use it as a variable at all tables? Or any other construct that will help me to avoid changing all the parameters?

I've seen such a code a while ago but I cant find this right now.

Answer 1

You could try this:

(* somewhere at the beginning of your code *)
Ts = Range[200,500,100];
ps = Range[1,4];

(* somewhere in the middle of your code -- version 1 *)
Table[T+p,{p,ps},{T,Ts}]

(* somewhere in the middle of your code -- version 2 *)
Table[Table[T+p,{T,Ts}],{p,ps}]

This works because one can let iteration variables run over a list, see the documentation for Table.

Answer 2

You may store the iteration variables in some variables and then insert them using "Evaluate". E.g.:

te = {temp, 200, 500, 100};
pr = {press, 1, 4};
Table[temp + press, Evaluate@te, Evaluate@pr]

(* {{201, 202, 203, 204}, {301, 302, 303, 304}, {401, 402, 403, 
  404}, {501, 502, 503, 504}}*)