Generate a prinicple component plot for a subset of genes, coloured by a given feature

subset_pc_plot(gene_set, exp.design, feature_label, counts.mat)

Arguments

gene_set	A vector containing gene names to subset
exp.design	Experimental design data frame
feature_label	Label in the data frame to facet by
counts.mat	Matrix containing expression count data

p A ggplot object containing the generated plot