compare2-class is used to store the results of multiple comparisons results,
including results for drawing and comparing differences between groups.
metaA data frame storing basic elements for visualization.
resultA data frame of multiple comparisons results.
tempA character vector of the difference comparison.
Users can construct a compare2-class through calc_compare2,
which can then be connected to nem_plot to visualize the results.
The constructor, calc_compare2; Class for storing single factor
multiple comparisons analysis, compare-class; Visualization function,
nem_plot.