Compute the linear-interpolated temperature compensation factor.

def cf_t(self, temp):
        """
        Compute the linear-interpolated temperature compensation factor.
        """
        index = int((temp - A4TempComp.__MIN_TEMP) // A4TempComp.__INTERVAL)        # index of start of interval

        # on boundary...
        if temp % A4TempComp.__INTERVAL == 0:
            return self.__values[index]

        # all others...
        y1 = self.__values[index]                                                   # y value at start of interval
        y2 = self.__values[index + 1]                                               # y value at end of interval

        delta_y = y2 - y1

        delta_x = float(temp % A4TempComp.__INTERVAL) / A4TempComp.__INTERVAL       # proportion of interval

        cf_t = y1 + (delta_y * delta_x)

        # print("A4TempComp.cf_t: alg:%d, temp:%f y1:%f y2:%f delta_y:%f delta_x:%f cf_t:%f " %
        #       (self.__algorithm, temp, y1, y2, delta_y, delta_x, cf_t), file=sys.stderr)

        return cf_t