Index related functions

Defined in xtensor/xoperation.hpp

template<class T>
auto xt::where(const T &condition)

return vector of indices where condition is true (equivalent to nonzero(condition))

Return

vector of index_types where condition is not equal to zero

Parameters

• condition: input array

template<class T>
auto xt::nonzero(const T &arr)

return vector of indices where T is not zero

Return

vector of vectors, one for each dimension of arr, containing the indices of the non-zero elements in that dimension

Parameters

• arr: input array

template<layout_type L = ::xt::layout_type::row_major, class T>
auto xt::argwhere(const T &arr)

return vector of indices where arr is not zero

Return

vector of index_types where arr is not equal to zero (use xt::from_indices to convert)

See

xt::from_indices

Template Parameters

• L: the traversal order

Parameters

• arr: input array

template<class T>
auto xt::from_indices(const std::vector<T> &idx)

Converts std::vector<index_type> (returned e.g.

from xt::argwhere) to xtensor.

Return

xt::xtensor<typename index_type::value_type, 2> (e.g. xt::xtensor<size_t, 2>)

Parameters

• idx: vector of indices