ggplot2 reverse log coordinate transform

revlog.R

## ggplot2 and mgcv for the plot
library(ggplot2)
library(mgcv)

## scales packages to define revlog
library(scales)

revlog_trans <- function(base = exp(1)){
    ## Define the desired transformation.
    trans <- function(x){
                 -log(x, base)
                }
    ## Define the reverse of the desired transformation
    inv <- function(x){
                 base^(-x)
                }
    ## Creates the transformation
    trans_new(paste("revlog-", base, sep = ""),
              trans, ## The transformation function (can be defined using anonymous functions)
              inv,  ## The reverse of the transformation
              log_breaks(base = base), ## default way to define the scale breaks
              domain = c(1e-100, Inf) ## The domain over which the transformation is valued
             )
    }

ggplot(philly.bw.count, aes(month.date, ndays/freq, color = race)) + 
    geom_point()+
    stat_smooth(method = gam, formula = y ~ s(x, bs = "cs"))+
    scale_y_continuous(name = "1 murder every X days",
                       breaks = c(0.5,1,2,7,14,21,31), 
                       trans = revlog_trans(base = 2))+ ## use the transformation we just created
    xlab("Date (by month)")+
    expand_limits(y = 0.5)+
    theme_bw()+
    scale_color_brewer(palette = "Set1")