$H_0$ from cosmic chronometers and Type Ia supernovae, with Gaussian
  Processes and the novel Weighted Polynomial Regression method
  In this paper we present new constraints on the Hubble parameter $H_0$ using:
(i) the available data on $H(z)$ obtained from cosmic chronometers (CCH); (ii)
the Hubble rate data points extracted from the supernovae of Type Ia (SnIa) of
the Pantheon compilation and the Hubble Space Telescope (HST) CANDELS and CLASH
Multy-Cycle Treasury (MCT) programs; and (iii) the local HST measurement of
$H_0$ provided by Riess et al. (2018), $H_0^{{\rm HST}}=(73.45\pm1.66)$
km/s/Mpc. Various determinations of $H_0$ using the Gaussian processes (GPs)
method and the most updated list of CCH data have been recently provided by Yu,
Ratra and Wang (2018). Using the Gaussian kernel they find $H_0=(67.42\pm
4.75)$ km/s/Mpc. Here we extend their analysis to also include the most
released and complete set of SnIa data, which allows us to reduce the
uncertainty by a factor $\sim 3$ with respect to the result found by only
considering the CCH information. We obtain $H_0=(67.06\pm 1.68)$ km/s/Mpc,
which favors again the lower range of values for $H_0$ and is in tension with
$H_0^{{\rm HST}}$. The tension reaches the $2.71\sigma$ level. We round off the
GPs determination too by taking also into account the error propagation of the
kernel hyperparameters when the CCH with and without $H_0^{{\rm HST}}$ are used
in the analysis. In addition, we present a novel method to reconstruct
functions from data, which consists in a weighted sum of polynomial regressions
(WPR). We apply it from a cosmographic perspective to reconstruct $H(z)$ and
estimate $H_0$ from CCH and SnIa measurements. The result obtained with this
method, $H_0=(68.90\pm 1.96)$ km/s/Mpc, is fully compatible with the GPs ones.
Finally, a more conservative GPs+WPR value is also provided, $H_0=(68.45\pm
2.00)$ km/s/Mpc, which is still almost $2\sigma$ away from $H_0^{{\rm HST}}$.
