R 更改条形图ggplot2中的内部图例顺序

我想在我的条形图中将图例顺序改为q1，中间值，q3，因为现在中间值是第一个命名的，这并不符合逻辑

barmedium <- ggplot(data=medium, aes(x=year, y=budgetresidual, group=Legend)) +
  geom_line(aes(linetype=Legend))+
  geom_point() +
  scale_linetype_manual(values=c("solid", "longdash", "dotted")) +
  scale_x_continuous(breaks = round(seq(min(medium$year), max(medium$year), by = 1),1),) +
  scale_y_continuous(breaks =c(-15,-10,-5,0,5,10), limits = c(-16,10)) +
  labs( x = "Year", y = "Budget residual") + theme_bw()
barmedium <- barmedium  + theme_update(legend.position='top')
barmedium 

---

barmedia尝试将图例列强制转换为一个按需重新排序的类别：

medium<- data.frame(
  stringsAsFactors = FALSE,
  year = c(2012L,2012L,2012L,2013L,2013L,2013L,
           2014L,2014L,2014L,2015L,2015L,2015L,2016L,
           2016L,2016L,2017L,2017L,2017L,2018L,
           2018L,2018L,2019L,2019L,2019L),
  Legend = c("q1","median","q3","q1","median","q3",
             "q1","median","q3","q1","median","q3",
             "q1","median","q3","q1","median","q3",
             "q1","median","q3","q1","median","q3"),
  budgetresidual = c(-8,-1,4,-9,-4,3,
                     -15,-9,1,-9,-3,
                     3,-12,-5,-0,-10,
                     -7,-2,0.2,3,8,-1,
                     3,6)
)

medium$Legend  <- factor(medium$Legend, levels = c("q1", "median", "q3"))
barmedium <- ggplot(data=medium, aes(x=year, y=budgetresidual, group=Legend)) +
  geom_line(aes(linetype=Legend))+
  geom_point() +
  scale_linetype_manual(values=c("solid", "longdash", "dotted")) +
  scale_x_continuous(breaks = round(seq(min(medium$year), max(medium$year), by = 1),1),) +
  scale_y_continuous(breaks =c(-15,-10,-5,0,5,10), limits = c(-16,10)) +
  labs( x = "Year", y = "Budget residual") + theme_bw()
barmedium <- barmedium  + theme_update(legend.position='top')
barmedium 

中等