Hi,

I'm trying to implement mean(). In Redux.h, it works:

Code: Select all

template
EIGEN_STRONG_INLINE typename ei_traits::Scalar
MatrixBase::mean() const
{
    NumTraits::Scalar>::Real n = size();
    return sum() / n;
}


In PartialRedux.h, however, this code gives a segfault...

Code: Select all

const CwiseUnaryOp::Real>, typename ReturnType::Type>
    mean() const
{
    NumTraits::Real n = (Direction==Vertical ? m_matrix.rows() : m_matrix.cols());
    return sum() / n;
}


Can anybody point me in the right direction? I've got no idea what I'm doing wrong.

Thanks!

marton wrote:In PartialRedux.h, however, this code gives a segfault...

Code: Select all

const CwiseUnaryOp::Real>, typename ReturnType::Type>
    mean() const
{
    NumTraits::Real n = (Direction==Vertical ? m_matrix.rows() : m_matrix.cols());
    return sum() / n;
}


Can anybody point me in the right direction? I've got no idea what I'm doing wrong.

Thanks!

this is because you return a temporary by reference. here is the fix:

Code: Select all

const CwiseUnaryOp::Real>, NestByValue::Type> >
    mean() const
{
    NumTraits::Real n = (Direction==Vertical ? m_matrix.rows() : m_matrix.cols());
    return sum().nestByValue() / n;
}


btw, one of the TODO item is a Statistic module where the goal would be to have such {matrix,column,row}-wise functions, just in case you are interested in starting it