zip_index() [2/2]

template<typename EigMat , typename IdxRows , typename IdxCols , require_eigen_matrix_dynamic_t< EigMat > * = nullptr, require_all_std_vector_t< IdxRows, IdxCols > * = nullptr>

var_value< Eigen::VectorXd > stan::math::zip_index ( const var_value< EigMat > &  x, IdxRows &&  idx_row, IdxCols &&  idx_col  )

inline

Return a column vector of matrix entries selected by paired one-based row and column indices.

Repeated index pairs accumulate adjoints in the same input entry.

Template Parameters

EigMat	Eigen matrix type inside the input var_value
IdxRows	Row index std::vector type with integer elements
IdxCols	Column index std::vector type with integer elements

Parameters

x	Input matrix
idx_row	Row indices
idx_col	Column indices

Returns

A var_value column vector with element i equal to x(idx_row[i] - 1, idx_col[i] - 1), or an empty vector for empty indices

Exceptions

std::invalid_argument	if the index vectors have different lengths
std::out_of_range	if an index is outside the matrix bounds

Definition at line 32 of file zip_index.hpp.