r - Error (ymax not found) while adding a geom_line (different data) to a multi-layered ggplot -

i'm trying generate plot summarizes dataset first plotting median & quantiles in area / black line, after want outline specific 'firm' red line.

i'd while facetting on variable, plotting multiple variables @ once.

an example code of i'd plot follows:

require(dplyr) require(ggplot2)  dt <- structure(list(firm = structure(c(1l, 1l, 1l, 1l, 1l, 1l, 2l,      2l, 2l, 2l, 2l, 2l, 3l, 3l, 3l, 3l, 3l, 3l, 4l, 4l, 4l, 4l, 4l,      4l), .label = c("a", "b", "c", "d"), class = "factor"), year = c(2008l,      2009l, 2008l, 2009l, 2008l, 2009l, 2008l, 2009l, 2008l, 2009l,      2008l, 2009l, 2008l, 2009l, 2008l, 2009l, 2008l, 2009l, 2008l,      2009l, 2008l, 2009l, 2008l, 2009l), variable = structure(c(1l,      1l, 2l, 2l, 3l, 3l, 1l, 1l, 2l, 2l, 3l, 3l, 1l, 1l, 2l, 2l, 3l,      3l, 1l, 1l, 2l, 2l, 3l, 3l), .label = c("var1", "var2", "var3"     ), class = "factor"), value = c(0.991894223, 2.216322113, 3.189415462,      0.663732077, 0.444826423, 2.674568191, 1.272077011, 7.691464914,      4.263339855, 0.214415839, 3.995328653, 6.028747322, 8.191459456,      0.16205906, 4.056495056, 5.17994524, 0.42435417, 0.678655669,      6.246411921, 0.505532339, 4.65045746, 8.85141854, 5.850616048,      2.028583225)), .names = c("firm", "year", "variable", "value"     ), class = "data.frame", row.names = c(na, -24l))  head(dt)    firm year variable     value 1     2008     var1 0.9918942 2     2009     var1 2.2163221 3     2008     var2 3.1894155 4     2009     var2 0.6637321 5     2008     var3 0.4448264 6     2009     var3 2.6745682 

i manually calculate ymin, ymax, , y ribbon / line plots. they're plotting fine.

dt_aggregates <- dt %>%   group_by(variable, year) %>%   arrange(variable, year) %>%   summarize(y=median(value)) dt_aggregates$ymin <- 0.9*dt_aggregates$y dt_aggregates$ymax <- 1.1*dt_aggregates$y 

this firm want highlight:

dt_focus <- filter(dt, firm=="a") 

the following plots fine, , want.

g <- ggplot(data=dt_aggregates,         aes(x=year,             y=y,            ymax=ymax,            ymin=ymin,            group=variable)) +    facet_grid(variable~., scales="free") + geom_line() + geom_ribbon(alpha=0.3) +   theme_bw()  

however, want add line (for 1 firm) onto (in red). once try add new line separate dataframe, following error. on getting work appreciated

# error in eval(expr, envir, enclos) : object 'ymax' not found g + geom_line(data=dt_focus,              aes(x=year, y=value, group=variable),             col="red", size=2)