#' This analysis was performed using [David](http://david.abcc.ncifcrf.gov/). The following ontologies were tested: `r paste(DEF_DAVID_ONTOLOGIES, collapse=', ')`
#' To understand spatio-temporal changes in gene expression better we now overlay enriched kegg pathways with the -log10(q_value) of each contrast. The direction of the expression changes is encoded as color, whereby red indicates that sample_1 is overexpressed. Because we have multiple contrasts of interest, this defines a slice-color barcode for each gene. To relate the barcode to contrasts we define the following slice order:
## todo why is tidyr not processing an empty dataframe