Add TemperatureResponse class

[dstansby]

The current implementation I'm using is below. This is useful for being able to sample a temperature response function, and in theory could be an anlytic function, or just interpolating between points.

class TemperatureResponse:
    """
    A discretely sampled temperature response function.

    Parameters
    ----------
    temps : astropy.units.Quantity
        Temperatures.
    responses : astropy.units.Quantity
        Response function.
    """
    # TODO: use astropy quantity input here
    def __init__(self, temps, responses):
        if temps.shape != responses.shape:
            raise ValueError('Shape of temps must be the same as '
                             'shape of responses')
        self.temps = temps
        self.responses = responses

    def __repr__(self):
        return f'TemperatureResponse, T={self.temps}, response={self.responses}'

    # TODO: use astropy quantity input here
    def sample(self, temps):
        """
        Sample the temperature repsonse function at temperatures *temps*.

        Uses linear interpolation.
        """
        resps = np.interp(temps, self.temps, self.responses,
                          left=np.nan, right=np.nan)
        return resps

[Cadair]

you might be able to use the Tabular1D model in astropy modelling to do this?

[wtbarnes]

This is a nice approach. I wonder if this could be the expected type for the temperature response input arguments to Model