用refine函数2次加密后的单元标号阵elem，可以看出总体节点编号的分布情况

 1 >> clear
 2 node = [1 1;-1 1;-1 -1;1 -1]; % nodes  squar
 3 elem = [1 2 3 4];    % elements
 4 belong=1:size(elem,1); bdEdge=[1 1 1 1];
 5 for k1=1:2
 6 [node,elem,bdEdge,HB,belong] = refine(node,elem,bdEdge,[],belong);
 7 end
 8 elem
 9 
10 elem =
11 
12      1    10    22    11
13      5    12    23    18
14      9    20    24    21
15      6    19    25    16
16     10     5    18    22
17     12     2    13    23
18     20     7    14    24
19     19     9    21    25
20     22    18     9    19
21     23    13     7    20
22     24    14     3    15
23     25    21     8    17
24     11    22    19     6
25     18    23    20     9
26     21    24    15     8
27     16    25    17     4