2</tt>). ARD with separate
length-scales for each input dimension is a very powerful tool to
learn which inputs are important for predictions: if length-scales are
short, inputs are very important, and when they grow very long
(compared to the spread of the data), the corresponding inputs will be
largely ignored. Both length-scales and the signal magnitude are
initialized to 1 (and represented in the log space). Finally, the
likelihood function <a href="../lik/likErf.m">likErf</a> has the shape
of the error