1.在下面找到我的解决方案，在geom_text(..., position, ...)中使用position_dodge(0.905)作为position参数的值
theme()在代码中与vjust=1, hjust=1无关，因为vjust=1, hjust=1已经是默认值。

df %>% 
  ggplot(aes(reorder(area, ammount), ammount,
             group = type,
             fill = type))+
  geom_col(position = "dodge")+
  scale_y_continuous(labels = comma_format(big.mark = ".",
                                           decimal.mark = ",")) +
  geom_text(aes(label = ammount), 
            size = 3, 
            position = position_dodge(0.905)) +
  coord_flip()

1. geom_text()有其他参数，如color, alpha，用于更改tex的颜色和可见性

df %>% 
  ggplot(aes(reorder(area, ammount), ammount,
             group = type,
             fill = type))+
  geom_col(position = "dodge")+
  theme(axis.text.x = element_text(vjust = 1, hjust=1))+
  scale_y_continuous(labels = comma_format(big.mark = ".",
                                           decimal.mark = ",")) +
  geom_text(aes(label = ammount), 
            size = 3, 
            position = position_dodge(0.8),
            color = 'darkblue',
            alpha = 1) +
  coord_flip()

可以找到更多文档here

1. ggplot2可能是完成这项任务的最佳软件包，但如果您需要交互式绘图，则可以考虑plotly和dygraph。

你可以试试这样的方法：

library(ggplot2)
library(magrittr)
library(scales)

df %>% 
  ggplot(aes(reorder(area, ammount), ammount,
             group = type,
             fill = type,
             # added label here
             label = ammount))+
  geom_col(position = "dodge")+
  scale_y_continuous(labels = comma_format(big.mark = ".",decimal.mark = ","))+
  theme(axis.text.x = element_text(vjust = 1, hjust=1))+
  # question 1, center labels, question 2, size to make more visible
  geom_text(position = position_dodge2(width = 0.9, preserve = "single"), size = 5)+
  xlab('area') +
  coord_flip()

结果：

对于你的第三个问题，有一个基数R，或者plotly用于交互式绘图。我很喜欢ggplot2，所以我不会搜索其他软件包。