麻烦大家帮我看看这段代码是什么意思？

漠漠之堡

1. function iid = distmat(X,dmax)
   
2. 
   
3. % constrained distance function
   
4. % iid -> [rows, columns, distance]
   
5. 
   
6. 
   
7. n     = size(X,1);%返回x的行数
   
8. nrdim = size(X,2);%返回x的列数（实验变差函数的计算维数）
   
9. if size(X,1) < 1000;
   
10.     [i,j] = find(triu(true(n)));
    
11.     if nrdim == 1;
    
12.         d = abs(X(i)-X(j));
    
13.     elseif nrdim == 2;
    
14.         d = hypot(X(i,1)-X(j,1),X(i,2)-X(j,2));
    
15.     else
    
16.         d = sqrt(sum((X(i,:)-X(j,:)).^2));
    
17.     end
    
18.     I = d<=dmax;
    
19.     iid = [i(I) j(I) d(I)];
    
20. else
    
21.     ix = (1:n)';
    
22.     if nrdim == 1;
    
23.         iid = arrayfun(@distmatsub1d,(1:n)','UniformOutput',false);
    
24.     elseif nrdim == 2;
    
25.         % if needed change distmatsub to distmatsub2d which is numerically
    
26.         % better but slower
    
27.         iid = arrayfun(@distmatsub,(1:n)','UniformOutput',false);
    
28.     else
    
29.         iid = arrayfun(@distmatsub,(1:n)','UniformOutput',false);
    
30.     end
    
31.     nn  = cellfun(@(x) size(x,1),iid,'UniformOutput',true);  
    
32.     I   = nn>0;
    
33.     ix  = ix(I);
    
34.     nn  = nn(I);
    
35.     nncum = cumsum(nn);
    
36.     c     = zeros(nncum(end),1);
    
37.     c([1;nncum(1:end-1)+1]) = 1;
    
38.     i = ix(cumsum(c));
    
39.     iid = [i cell2mat(iid)];
    
40.    
    
41. end
    
42. 
    
43. function iid = distmatsub1d(i)
    
44.     j  = (i+1:n)';
    
45.     d  = abs(X(i)-X(j));
    
46.     I  = d<=dmax;
    
47.     iid = [j(I) d(I)];
    
48. end
    
49. 
    
50. function iid = distmatsub2d(i)  %#ok<DEFNU>
    
51.     j  = (i+1:n)';
    
52.     d = hypot(X(i,1) - X(j,1),X(i,2) - X(j,2));
    
53.     I  = d<=dmax;
    
54.     iid = [j(I) d(I)];
    
55. end
    
56.    
    
57. function iid = distmatsub(i)
    
58.     j  = (i+1:n)';
    
59.     d = sqrt(sum(bsxfun(@minus,X(i,:),X(j,:)).^2,2));
    
60.     I  = d<=dmax;
    
61.     iid = [j(I) d(I)];
    
62. end
    
63. end

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ChaChing

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