Tell me how to implement a custom regression model in sktime using the formula:
An example of my code implementing a model in scipy:
from scipy.optimize import curve_fit
def model_func(x, b0: float, b1: float, b2: float, b3: float, b4: float) -> np.array:
days: np.array = x[0]
t: np.array = x[1]
H: np.array = x[2]
c: int = 18
HDD: np.array = np.maximum(c-t, 0)
CDD: np.array = np.maximum(t-c, 0)
return b0 + b1*HDD + b2*CDD + b3*H + b4*days
popt, pcov = curve_fit(model_func, xdata , ydata)
