HeatMap, problems with the scale color and dendrogram

Hi,

I am trying to make a Heatmap of some analyzed RNAseq data. I am using ggplot2 with R. The problem I have is that I cannot see well the upregulated and the downregulated genes. I can’t get the colors shown to be dark enough. I am doing the heatmap with all the genes of the study organism, around 13,000. I’m also not sure that ggplot2 clusters the genes in my data. Is there a way to cluster the genes and see darker colors in the genes upregulated and the downregulated? The code I am using would be the following:

library(ggplot2) 
library(reshape2)

g<-read.csv("datos_prueba3.csv") g3<-melt(g)

plot1 <- ggplot(g3, aes(variable, Gene, fill=value)) + geom_tile() + scale_fill_gradient2(low="dark green", high="dark red", mid="green", midpoint=0) + theme(axis.text.y=element_blank()) 
plot1

Best,