This is the plot method for objects
  of class "quadrattest". Such an object is produced by
  quadrat.test and represents the result of
  a \(\chi^2\) test for a spatial point pattern.
The quadrats are first plotted using plot.tess.
  Then in each quadrat, the observed and expected counts
  and the Pearson residual are displayed as text using
  text.default.
  Observed count is displayed at top left; expected count at top right;
  and Pearson residual at bottom.