def _det(xvert, yvert):
    '''Compute twice the area of the triangle defined by points with using
    determinant formula.

    Input parameters:

    xvert -- A vector of nodal x-coords (array-like).
    yvert -- A vector of nodal y-coords (array-like).

    Output parameters:

    Twice the area of the triangle defined by the points.

    Notes:

    _det is positive if points define polygon in anticlockwise order.
    _det is negative if points define polygon in clockwise order.
    _det is zero if at least two of the points are concident or if
        all points are collinear.

    '''
    xvert = np.asfarray(xvert)
    yvert = np.asfarray(yvert)
    x_prev = np.concatenate(([xvert[-1]], xvert[:-1]))
    y_prev = np.concatenate(([yvert[-1]], yvert[:-1]))
    return np.sum(yvert * x_prev - xvert * y_prev, axis=0)
Compute twice the area of the triangle defined by points with using
    determinant formula.

    Input parameters:

    xvert -- A vector of nodal x-coords (array-like).
    yvert -- A vector of nodal y-coords (array-like).

    Output parameters:

    Twice the area of the triangle defined by the points.

    Notes:

    _det is positive if points define polygon in anticlockwise order.
    _det is negative if points define polygon in clockwise order.
    _det is zero if at least two of the points are concident or if
        all points are collinear.

    
recipes/Python/578381_pointinpolygprogram_SW/recipe-578381.py