Question

我有以下矩阵：

M =[ 0  0  0  0  0  0  0  0 ;
     0  0  0  0  0  0  6  0 ;
     0  0  0  0  3  0  3  3 ;
     0  0  0  9  9  6  9  6 ;
     0  0  0  9  6  9  9  0 ;
     0  0  0  0  6  3  0  0 ;
     0  0  0  0  0  0  0  0 ;
     0  0  0  0  0  0  0  0 ];

我希望在1的10个随机选择的元素中添加M，其中0大于DECLARE @fileLocation VARCHAR(128) = 'c:\foldername\' --DECLARE @fileName VARCHAR(128) --------------------------------------------------------------------------------------------------------------- --Get a list of all the file names in the directory --------------------------------------------------------------------------------------------------------------- IF OBJECT_ID('tempdb..#FileNames') IS NOT NULL DROP TABLE #FileNames CREATE TABLE #FileNames ( id int IDENTITY(1,1) ,subdirectory nvarchar(512) ,depth int ,isfile bit ,LogTime datetime null) INSERT #FileNames (subdirectory,depth,isfile) EXEC xp_dirtree @fileLocation, 1, 1。

怎么做？

Answer 1

查找大于零的元素的索引，并从那些将递增的索引生成n个随机样本。然后，只需将1添加到n个随机索引的元素中。

n=10;           %No. of elements of M greater than zero which will be incremented by 1
t1 = find(M>0); %Finding indices of elements of M which are greater than zero
t2 = randperm(length(t1)); %Generating random indices from which first n will be selected
M(t1(t2(1:n))) = M(t1(t2(1:n)))+1  %Incrementing elements of random n indices

如果您有统计和机器学习工具箱，则可以使用以下更简单的方法解决方案使用randsample：

n=10; 
temp = randsample(find(M>0),n);
M(temp) = M(temp)+1

Answer 2

您可以通过创建非零元素位置的随机排列来选择要增加的元素。

m = 10;   % we want to increment 10 elements
elements = find(M);   % positions of the nonzero elements
rand_order = randperm(numel(elements), m);   % generate random permutation
M(elements(rand_order)) = M(elements(rand_order)) + 1;

randperm确保每个非零元素只能以随机顺序选择一次。

如何增加一些大于零的随机选择的元素？

2 个答案: