在for循环中使用facet_grid（）的geom_text（）

Question

我正在使用ggplot2创建多个图表，并使用facet_grid（）按年分类。我想在每个特定年份添加文本，总值低于0.但是，如果没有数据，我不希望出现一年（参见下面的示例）。图表b应该只显示2015年，因为它没有2016年的数据。我也有重复文本的问题（即使我已经指定了一个特定的标签）。

year <- c(2015,2015,2015,2016,2016,2016,2015,2015,2015)
group <- c("a","a","a","a","a","a","b","b","b")
value <- c(-10,20,0,10,20,0,-10,5,15)

df <- as.data.frame(cbind(year,group,value))
df$value <- as.numeric(as.character(df$value))

y <- split(df, df$group)

i=1
for (i in 1:length(y)) {

    y[[i]] <- y[[i]][order(y[[i]]$year,y[[i]]$value),]


    p <- ggplot(y[[i]], aes(seq(1,nrow(y[[i]]),by=1),value))+
         geom_area(position="identity", alpha=0.5)+
         ggtitle(paste0(names(y[i])))+
         ylab("value")+
         facet_grid(year~.)+ 
         xlab("")

    #get subsets for adding totals by year
    all_15 <- subset(y[[i]],y[[i]]$year == 2015)
    all_15$value <- as.numeric(as.character(all_15$value))

    all_16 <- subset(y[[i]],y[[i]]$year == 2016)
    all_16$value <- as.numeric(as.character(all_16$value))


    #total below by year
    below15 <- paste0("Total Cost Below - ", round(abs(sum(all_15$value[all_15$value<0])),2))
    below16 <- paste0("Total Cost Below - ", round(abs(sum(all_16$value[all_16$value<0])),2))

    #add text to show total below for each year
    ann_text <- data.frame(-Inf, value=-Inf,lab = below15,
                           year = factor(2015,levels = c(2015,2016)))

    ann_text2 <- data.frame(-Inf, value=-Inf,lab = below16,
                            year = factor(2016,levels = c(2015,2016)))

    q <- p + geom_text(data = ann_text,label = ifelse(nrow(y[[i]][y[[i]]$year == 2015,])>1,levels(ann_text$lab), ""), hjust = 0, vjust = -1) 
    q2 <- q + geom_text(data = ann_text2,label = ifelse(nrow(y[[i]][y[[i]]$year == 2016,])>1,levels(ann_text2$lab), ""), hjust = 0, vjust = -1)

    print(q2)

}

第一张图 第二张图