r - Exclude unused factor levels in each facet in ggplot -

consider data frame:

df <- data.frame(vars=c(rnorm(3),rnorm(3,2,1), rnorm(3,1,1)),              names=c("a","b","c","a","d","b","c","a","f"),              groups=c(rep("x",3),rep("y",3),rep("z",3))) 

i'm plotting ggplot:

ggplot(df, aes(reorder(names, vars), names)) +    geom_bar(stat="identity") + theme_bw() + facet_grid(groups~., scales="free_x") + coord_flip() +     ylab(null) + xlab(null) 

it looks

i want following:

• each grid item should drop unused items, e.g. in "x" grid there should no "d" , "f"
• the x axis should the value of "vars" column. proportions in each grid should same, overall x scale should dropped. want proportions of bars in each grid intact
• the bars should in decreasing order in each grid (longer bars on top)

update:

edit using advice here error:

ggplot(df, aes(names,vars)) + geom_bar(stat="identity") + coord_flip() +    theme_bw() + facet_wrap(~groups,nrow = 3,scales = "free_x")  error in facet_render.wrap(plot$facet, panel, plot$coordinates, theme,  :    ggplot2 not support free scales non-cartesian    coord or coord_flip. in addition: warning message: stacking not defined when ymin != 0  

when remove coord_flip() works still warning , result not want.

this bit of workaround gives plot plot seems meet basic objectives. geom_bar replaced geom_seqment because seems closer you're plotting , avoids complications of coord_flip. order of bars determined rank of vars in each group. y axis labels can't specified directly can use geom_text place proper names values next y axis these act labels. also, switched facet label left side seemed improve overall appearance of facet , y axis labels.

set.seed(177) df <- data.frame(vars=c(rnorm(3),rnorm(3,2,1), rnorm(3,1,1)),                  names=c("a","b","c","a","d","b","c","a","f"),                  groups=c(rep("x",3),rep("y",3),rep("z",3)))  library(ggplot2) sp1 <- ggplot(data=transform(df, ranked=ave(vars, groups, fun=rank)),                   aes( x=vars, y=ranked)) sp1 <- sp1 + geom_segment( aes( xend = 0,  yend = ranked), size=10) sp1 <- sp1 + geom_text( aes( x = min(vars), y= ranked, label = names), hjust= 4) sp1 <- sp1 + scale_y_discrete(label=null) sp1 <- sp1 + theme_bw() sp1 <- sp1  + facet_grid( groups ~ .,  scales="free", switch="y") plot(sp1) 

plot looks like