How to plot p-values in a circular barplot? Im trying to plot reactome pathway in for of circular bar plot using ggplot2 

my data

    dput(df2)
structure(list(ID = 1:10, Pathway_names = structure(c(5L, 1L, 
7L, 6L, 2L, 3L, 9L, 8L, 10L, 4L), .Label = c("Antigen Presentation: Folding assembly and peptide loading of class I MHC", 
"Antigen processing-Cross presentation", "Class I MHC mediated antigen processing &amp; presentation", 
"Cytokine Signaling in Immune system", "Endosomal/Vacuolar pathway", 
"ER-Phagosome pathway", "Immunoregulatory interactions between a Lymphoid and a non-Lymphoid cell", 
"Interferon alpha/beta signaling", "Interferon gamma signaling", 
"Interferon Signaling"), class = "factor"), Entities_found = structure(c(1L, 
2L, 3L, 4L, 4L, 5L, 6L, 7L, 8L, 9L), .Label = c("51", "54", "55", 
"57", "75", "77", "96", "117", "176"), class = "factor"), Entities_pValue = c(1.11e-16, 
1.11e-16, 0.003908431, 2.54e-12, 2.77e-10, 0.0053068, 1.64e-13, 
1.11e-16, 1.11e-16, 3.68e-06)), row.names = c(NA, -10L), class = "data.frame")


my code 

ggplot(df2, aes(x = factor(Pathway_names), y = Entities_found)) + ######################################
  geom_bar(aes(fill = Entities_pValue), stat = "identity", position = "stack") + 
  #scale_fill_manual(values = c(blank = "white", dark = "black")) + 
  coord_polar() + 
  theme_minimal() + 
  guides(fill = FALSE)




So far im not sure how to include both p value and entities in the plot so that the pathway that are coming up can be labeled accordingly 

New figure
The adjustcolor function from grDevices can be used to generate colours with transparency. What you want is colours based on the pathway and transparency to form a colour gradient for the p-value.

adjustcolor( "red", alpha.f = 0.2)

For the ggplot example, the aes function has an alpha parameter.

ggplot(df2, aes(x = factor(Pathway_names), y = Entities_found), alpha = Entities_pValue) + ######################################
geom_bar(aes(fill = Entities_found, alpha = Entities_pValue), stat = "identity", position = "stack") +  
coord_polar() + 
theme_minimal() + 
 guides(fill = FALSE)