#ifndef STAN_MATH_PRIM_MAT_FUN_SD_HPP
#define STAN_MATH_PRIM_MAT_FUN_SD_HPP

#include <stan/math/prim/arr/err/check_nonzero_size.hpp>
#include <stan/math/prim/mat/fun/Eigen.hpp>
#include <stan/math/prim/mat/fun/variance.hpp>
#include <boost/math/tools/promotion.hpp>
#include <vector>

namespace stan {
  namespace math {

    /**
     * Returns the unbiased sample standard deviation of the
     * coefficients in the specified column vector.
     * @param v Specified vector.
     * @return Sample variance of vector.
     */
    template <typename T>
    inline
    typename boost::math::tools::promote_args<T>::type
    sd(const std::vector<T>& v) {
      check_nonzero_size("sd", "v", v);
      if (v.size() == 1) return 0.0;
      return sqrt(variance(v));
    }

    /**
     * Returns the unbiased sample standard deviation of the
     * coefficients in the specified vector, row vector, or matrix.
     * @param m Specified vector, row vector or matrix.
     * @return Sample variance.
     */
    template <typename T, int R, int C>
    inline
    typename boost::math::tools::promote_args<T>::type
    sd(const Eigen::Matrix<T, R, C>& m) {
      check_nonzero_size("sd", "m", m);
      if (m.size() == 1) return 0.0;
      return sqrt(variance(m));
    }

  }
}
#endif
