Matlab将一行的第一列匹配为索引，然后平均该行中的所有列 [英] Matlab matching first column of a row as index and then averaging all columns in that row

问题描述

在获取以下数据时，我需要帮助，这些数据以大矩阵进行组织，并对具有匹配ID(索引)的所有值求平均值，并输出仅包含ID和跟踪它的平均值的另一个矩阵.

I need help with taking the following data which is organized in a large matrix and averaging all of the values that have a matching ID (index) and outputting another matrix with just the ID and the averaged value that trail it.

File with data format:
(This is the StarData variable)
ID>>>>Values

002141865 3.867144e-03  742.000000  0.001121  16.155089  6.297494  0.001677

002141865 5.429278e-03  1940.000000  0.000477  16.583748  11.945627  0.001622

002141865 4.360715e-03  1897.000000  0.000667  16.863406  13.438383  0.001460

002141865 3.972467e-03  2127.000000  0.000459  16.103060  21.966853  0.001196

002141865 8.542932e-03  2094.000000  0.000421  17.452007  18.067214  0.002490

请不要误解我发布的示例，第一个数字重复大约15行，然后ID更改，然后重复整个不同ID的集合，然后再次将它们作为一个整体重复，请考虑一下第一个块的代码= [1 2 3; 1 5 9; 2 5 7; [2 4 6]，然后代码将为索引重复不同的列值(索引除外).主要的区别是，值跟在我需要在matlab中平均的ID后面，并输出一个干净的矩阵，其中每个ID中只有一个ID对于所有出现的ID均被完全平均. 感谢您提供的任何帮助.

Do not be mislead by the examples I posted, that first number is repeated for about 15 lines then the ID changes and that goes for an entire set of different ID's, then they are repeated as a whole group again, think first block of code = [1 2 3; 1 5 9; 2 5 7; 2 4 6] then the code repeats with different values for the columns except for the index. The main difference is the values trailing the ID which I need to average out in matlab and output a clean matrix with only one of each ID fully averaged for all occurrences of that ID. Thanks for any help given.

推荐答案

对此答案所做的修改，如下:

[value_sort ind_sort] = sort(StarData(:,1));
[~, ii, jj] = unique(value_sort);
n = diff([0; ii]);
averages = NaN(length(n),size(StarData,2)); % preallocate
averages(:,1) = StarData(ii,1);
for col = 2:size(StarData,2)
  averages(:,col) = accumarray(jj,StarData(ind_sort,col))./n;
end

结果在变量averages中.它的第一列包含用作索引的值，随后的每一列包含根据索引值对该列的平均值.

The result is in variable averages. Its first column contains the values used as indices, and each subsequent column contains the average for that column according to the index value.

Matlab 2013a以后的兼容性问题:

函数unique在Matlab中已已更改 2013a.从该版本开始，将'legacy'标志添加到unique，即，将第二行替换为

The function unique has changed in Matlab 2013a. For that version onwards, add 'legacy' flag to unique, i.e. replace second line by

[~, ii, jj] = unique(value_sort,'legacy')

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