当我使用2个print ggplot命令获取R文件时，为什么没有出现第一个图？

Question

g.rank <- ggplot(data = train, aes(Result, RankDiff)) +
          geom_boxplot(fill = c("#FFF59D", "#EF9A9A", "#A5D6A7")) 
print(g.rank)

g.diff <- ggplot(data = train, aes(Result, DiffDiff)) +
          geom_boxplot(fill = c("#FFF59D", "#EF9A9A", "#A5D6A7")) 
print(g.diff)

当我获取包含上述代码的R文件时，第一个绘图不会出现在Rstudio的绘图历史中。