r - Density of each group of weighted geom_density sum to one -

how can group density plot , have density of each group sum one, when using weighted data?

the ggplot2 geom_density() suggests hack using weighted data: dividing sum of weights. when grouped, means combined density of groups totals one. density of each group total one.

i have found 2 clumsy ways this. first treat each group separate dataset:

m <- ggplot() m + geom_density(data = movies[movies$action == 0, ], aes(rating, weight = votes/sum(votes)), fill=na, colour="black") +     geom_density(data = movies[movies$action == 1, ], aes(rating, weight = votes/sum(votes)), fill=na, colour="blue") 

obvious disadvantages manual handling of factor levels , aesthetics. tried using windowing functionality of data.table package create new column total votes per action group, dividing instead:

movies.dt <- data.table(movies) setkey(movies.dt, action) movies.dt[, votes.per.group := sum(votes), action] m <- ggplot(movies.dt, aes(x=rating, weight=votes/votes.per.group, group = action, colour = action)) m + geom_density(fill=na) 

are there neater ways this? because of size of tables, i'd rather not replicate rows weighting sake of using frequency.

i think auxillary table might option. had similar problem here. issue seems that, when ggplot uses aggregating functions in aes(...), applies them whole dataset, not subsetted data. when write

aes(weight=votes/sum(votes)) 

the votes in numerator subsetted based on action, votes in denominator, sum(votes), not. same true implicit grouping facets.

if else has way around i'd love hear it.