1 #ifndef STAN_MATH_PRIM_FUN_ROW_HPP
2 #define STAN_MATH_PRIM_FUN_ROW_HPP
3 
4 #include <stan/math/prim/err.hpp>
5 #include <stan/math/prim/fun/Eigen.hpp>
6 
7 namespace stan {
8 namespace math {
9 
10 /**
11  * Return the specified row of the specified matrix, using
12  * start-at-1 indexing.
13  *
14  * This is equivalent to calling <code>m.row(i - 1)</code> and
15  * assigning the resulting template expression to a row vector.
16  *
17  * @tparam T type of the matrix
18  * @param m Matrix.
19  * @param i Row index (count from 1).
20  * @return Specified row of the matrix.
21  * @throw std::out_of_range if i is out of range.
22  */
23 template <typename T, require_matrix_t<T>* = nullptr>
row(const T & m,size_t i)24 inline auto row(const T& m, size_t i) {
25   check_row_index("row", "i", m, i);
26 
27   return m.row(i - 1);
28 }
29 
30 }  // namespace math
31 }  // namespace stan
32 
33 #endif
34