txt文件的内容是：'Node 3: (98.797470,86.414753,10.000000)' 'Node 9: (88.440505,72.085567,10.000000)' 'Node 1: (65.385059,40.672692,10.000000)' 'Node 5: (45.039358,20.567234,10.000000)' 'Node 7: (28.338438,89.619886,10.000000)' 'Node 2: (7.205155,66.693153,10.000000)' 'Node 8: (83.436900,60.962969,10.000000)' 'Node 4: (88.283761,91.371168,10.000000)' 'Node 10: (11.703682,81.468169,10.000000)' 'Node 6: (67.322599,66.427990,10.000000)' 'Node 14: (9.537269,14.651486,10.000000)' 'Node 13: (8.424705,16.389832,10.000000)' 'Node 12: (95.091520,72.234851,10.000000)' 'Node 11: (54.655379,56.192015,10.000000)' 'Node 15: (99.685021,55.354157,10.000000)' 'Node 19: (20.207510,45.389347,10.000000)' 'Node 18: (89.786568,59.336186,10.000000)' 'Node 17: (61.347488,81.864074,10.000000)' 'Node 16: (7.103708,88.773922,10.000000)' 'Node 20: (72.016461,34.689519,10.000000)' fid = fopen('node_coordinates.txt', 'r'); data = textscan(fid, '%f %f %f %f', 'HeaderLines', 1); fclose(fid); node_id = data{1};但是在[~, idx] = sort(BC,'descend'); top_nodes = node_id(idx(1:3));出现了索引超出数组范围，这是为什么，怎么修改

这个错误可能是因为 `BC` 数组的长度小于你想要取的前三个最大值的数量，所以 `idx` 中有一些索引超出了 `BC` 数组的范围。为了避免这个问题，你可以添加一个条件判断来检查 `BC` 数组的长度是否足够，例如：

[~, idx] = sort(BC,'descend');
if length(BC) >= 3
   top_nodes = node_id(idx(1:3));
else
   disp('BC数组长度不足3');
end

这样，如果 `BC` 数组的长度小于3，将会输出一条错误信息，而不会导致程序崩溃。