Описание тега array-indexing
Use this tag for questions about how to construct and interpret indices for retrieval of or assignment to non-trivial subsets or reorderings of multidimensional arrays.
Arrays are usually indexed numerically along their different dimensions. However, some packages, like numpy and MATLAB, allow for more complex objects to be used to compute the numerical indices. Questions with this tag should refer to such non-trivial indices. Examples include boolean masks, lists of integers (which behave differently in different languages), and linear indices into a multidimensional array.