This function takes the output of .RNAseq_all_gene() function and generate
box plots of differential gene expression across all TCGA cancer types
This function should not be used directly,
only inside .plot_boxgraph_RNAseq_TCGA()function.
Side effect: box plots on screen and as pdf file to compare relative expression of EIF genes across all TCGA cancer type
.RNAseq_grouped_boxplot(df)output dataset from .RNAseq_all_gene(.TCGA_GTEX_RNAseq_sampletype_subset),
which was generated inside .plot_boxgraph_RNAseq_TCGA()function.
Other helper function for differential expression plotting:
.RNAratio_boxplot(),
.RNAseq_boxplot(),
.violinplot()