sd.hpp

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#ifndef STAN__MATH__MATRIX__SD_HPP
#define STAN__MATH__MATRIX__SD_HPP

#include <vector>
#include <boost/math/tools/promotion.hpp>
#include <stan/math/matrix/Eigen.hpp>
#include <stan/math/matrix/variance.hpp>
#include <stan/math/error_handling/matrix/check_nonzero_size.hpp>

namespace stan {
  namespace math {
    
    template <typename T>
    inline 
    typename boost::math::tools::promote_args<T>::type
    sd(const std::vector<T>& v) {
      stan::math::check_nonzero_size("sd(%1%)",v,"v",(double*)0);    
      if (v.size() == 1) return 0.0;
      return sqrt(variance(v));
    }

    template <typename T, int R, int C>
    inline 
    typename boost::math::tools::promote_args<T>::type
    sd(const Eigen::Matrix<T,R,C>& m) {
      // FIXME: redundant with test in variance; second line saves sqrt
      stan::math::check_nonzero_size("sd(%1%)",m,"m",(double*)0);    
      if (m.size() == 1) return 0.0;
      return sqrt(variance(m));
    }    
    
  }
}
#endif