density plot with disparate scaling

RH_ds2_long_density.r

library(ggplot2)
library(dplyr)
library(cowplot)
theme_set(theme_cowplot())
load("ds2_long.rdata")

# Smith is different than the other two
combine_ds2_long %>% split(.$study) %>% lapply(function(x) summary(x$value)) %>% bind_rows
# Min.      `1st Qu.`  Median    Mean         `3rd Qu.` Max.     `NA's` 
# <table>   <table>    <table>   <table>      <table>   <table>  <table>
#  8.82e-65 1.0000e-03 3.300e-02 1.585343e-01 2.31e-01  9.94e-01 414    
#  6.39e-12 8.6000e-02 3.120e-01 3.788611e-01 6.43e-01  9.99e-01 221    
# 7.59e-165 6.9025e-14 2.285e-10 4.042874e-09 4.51e-09  3.15e-08 414 

density<-ggplot(combine_ds2_long) +
  aes(x=value,colour=study,fill=study) +  
  geom_density(position="identity") +
  facet_wrap(~study, scale="free")

density_zscore <- combine_ds2_long %>% group_by(study) %>% mutate(value_z=scale(value)) %>%
 ggplot() +
  aes(x=value_z,colour=study,fill=study) +  
  geom_density(alpha=.4)

plot_grid(density,density_zscore, nrow=2)