  Facing the world wide coronavirus disease 2019 (COVID-19) pandemic, a new
fitting method (QDF, quasi-distribution fitting) which could be used to analyze
the data of COVID-19 is developed based on piecewise quasi-uniform B-spline
curves. For any given country or district, it simulates the distribution
histogram data which is made from the daily confirmed cases (or the other data
including daily recovery cases and daily fatality cases) of the COVID-19 with
piecewise quasi-uniform B-spline curves. Being dealt with area normalization
method, the fitting curves could be regarded as a kind of probability density
function (PDF), its mathematical expectation and the variance could be used to
analyze the situation of the coronavirus pandemic. Numerical experiments based
on the data of certain countries have indicated that the QDF method demonstrate
the intrinsic characteristics of COVID-19 data of the given country or distric,
and because of the interval of data used in this paper is over one year (500
days), it reveals the fact that after multi-wave transmission of the
coronavirus, the case fatality rate has declined obviously, the result shows
that as an appraisal method, it is effective and feasible.
