Creates a Principal Components plot where we can show paired samples,
and confidence intervals for the mean of every group of interest.
We can also choose the component or components we want to plot.
Variable in pData(x) that contains the groups of interest. Samples
of the same group will be plotted with the same color.
group2
Variable in pData(x) that contains secondary groups of
interest. Sample of the same secondary group of interest will be
plotted with the same symbol.
pair
Variable in pData(x) that contains the information about the pairs
of data. Those pairs will be joined by a line.
names
Variable in pData(x) that contains the information about the names
of the samples.
ellipse
If we want to plot ellipses with the 95 percent confidence intervals
for every group.
main
A title for the plot.
components
Which components we want to plot. By default the first principal
component will be plotted on the x axis and the second principal
component will be plotted on the y axis.
More than two components may be specified. If so multiple plots will
be produced.