adjust the scale in ggplot [duplicate]

Question

Possible Duplicate:
automatic non-equidistant breaks in ggplot2

I am creating a ggplot2 heat map chart. My Data is as follows:

df    

 Date    Value     Desc
1/1/2012 40       Brasil
1/1/2012  90      Argentina
1/1/2012  10      England
1/1/2012   5      China
2/1/2012 40       Brasil
2/1/2012  90      Argentina
2/1/2012  10      England
2/1/2012   24      China
3/1/2012 40       Brasil
3/1/2012  90      Argentina
3/1/2012  10      England
1/1/2012   0      China


ggplot(df, aes(Date, Desc, fill=Value)) + geom_tile(colour="white") + scale_fill_gradient(low="white", high="red"")

ggplot comes up with its default scale from 10 to 50 etc on the right as legend. How can I manually alter this? Rather than having 10, 15, 20, 60 etc. I like to have lowest to highest with break points?

Answer 1

You want the breaks argument I think. see ?scale_fill_gradient for a description:

ggplot(df, aes(Date, Desc, fill=Value)) + 
  geom_tile(colour="white") + 
  scale_fill_gradient(low="white", 
                      high="red", 
                      breaks=seq(min(df$Value), max(df$Value), by=30))