COVID19: what is the growth rate?

Answer: the growth rate is about 1.3 per day for Europe and US. This means a doubling of the number of cases every 2-3 days. Slower for Japan and Singapore. South Korea also shows signs of slower growth. More in depth about the method below the graphs.

Method

data: john hopkins via kaggle as of 2020-03-07

Cases are reported daily. 

The model applied is least squares on the logarithm of number of cases. The code:

	def exponential_regression(cases):
	"""
	Fitting parameters alpha and beta to
	cases = beta * t ^ (alpha)
	where t is number of samples (days) since the start.
	"""
	N = len(cases)
	A = np.ones([N, 2])
	A[:, 0] = list(range(N))
	b = np.log(cases)
	res = np.linalg.lstsq(A, b, rcond=None)
	alpha, beta = res[0]
	alpha = np.exp(alpha)
	beta = np.exp(beta)
	return alpha, beta

view raw exponential_regression.py hosted with ❤ by GitHub

The model is applied from the when there is at least 70 reported cases.