H = showeqbox(F) shows the equation box of the fit F, using the settings
defined in fitparam. The fit structure F is obtained from ezfit. H is a
handle to the equation box.
Note that showeqbox interprets the greek symbols in the fitting equation
(latex syntax). The '\' latex symbol must be omitted.
showeqbox is automatically called from showfit or SELECTFIT when the
option 'dispeqboxmode' is set to 'on' in the fitparam.m file.
f = ezfit('alpha/x^n');