sorting - R ggplot ordering bars in "barplot-like " plot

Question

This is my code:

ggplot(tmp, aes(x=tmp$V2, y=-log10(tmp$V3), fill=tmp$V1)) +
geom_bar(stat="identity") +
coord_flip()

Now I would like to create the same plot as above but where the values within each "groups" are sorted. Something that will look like this.

Answer 1

You can order the variable by converting it into factor.

> head(d)
                     V1                                     V2       V3
1 GO Biological Process  regulation of lipid metabolic process 1.87e-35
2 GO Biological Process            acute inflammatory response 3.21e-37
3 GO Biological Process           response to insulin stimulus 1.05e-38
4 GO Biological Process              steroid metabolic process 4.19e-39
5 GO Biological Process          cholesterol metabolic process 1.19e-40
6 GO Biological Process cellular response to chemical stimulus 5.87e-42

> d$V4 <- factor(d$V2, levels=d$V2) # convert V2 into factor
> head(d)
                     V1                                     V2       V3                                     V4
1 GO Biological Process  regulation of lipid metabolic process 1.87e-35  regulation of lipid metabolic process
2 GO Biological Process            acute inflammatory response 3.21e-37            acute inflammatory response
3 GO Biological Process           response to insulin stimulus 1.05e-38           response to insulin stimulus
4 GO Biological Process              steroid metabolic process 4.19e-39              steroid metabolic process
5 GO Biological Process          cholesterol metabolic process 1.19e-40          cholesterol metabolic process
6 GO Biological Process cellular response to chemical stimulus 5.87e-42 cellular response to chemical stimulus

> # plot
> ggplot(d, aes(V4, -log10(V3), fill=V1)) + geom_bar() + coord_flip()

here is further information: http://kohske.wordpress.com/2010/12/29/faq-how-to-order-the-factor-variables-in-ggplot2/