def linear(target, m, b, prop):
    """
    Calculates a property as a linear function of a given property

    Parameters
    ----------
    target : OpenPNM Object
        The object for which these values are being calculated.  This
        controls the length of the calculated array, and also provides
        access to other necessary thermofluid properties.

    m, b : floats
        Slope and intercept of the linear corelation

    prop : string
        The dictionary key containing the independent variable or phase
        property to be used in the correlation.

    Returns
    -------
    value : NumPy ndarray
        Array containing ``m * target[prop] + b``.

    """
    x = target[prop]
    value = m * x + b
    return value
