  The subset selection problem of linear algebra is applied to identify
independent patterns of COVID-19 evolution within Brazil. The data consist of a
set of mortality curves in states of Brazil. A subset of the most independent
curves is selected by using a functional version of the QR matrix decomposition
technique with column pivoting. The selected subset is used next as a basis to
represent the remaining curves filtering out any data redundancy. For each
independent curve, an associated epidemiological region of influence is
defined. The results show two main independent curves with a similar two-peak
pattern and a 50-day shift between the patterns. Two main epidemiological
regions are next identified: one encompassing most of the country from the
center and northeast states to the south, an another one containing the
Amazonian region at the northwest.
