ggplot2：修改散点图 {ggplot2} 中两个因素的图例元素？

Question

我希望我的散点图显示两个因素：点大小和灰色阴影:

a1<-c(seq(1,10,1))
a2<-c(seq(11,20,1))
a3<-c(rep(c(1,2),each = 5))
a4<-c(rep(c(5,10,15,20,25),2))

df<-data.frame(a1,a2,a3,a4)

t1<-theme(        
  plot.background = element_blank(), 
  panel.grid.major = element_blank(), 
  panel.grid.minor = element_blank(), 
  panel.border = element_blank(), 
  panel.background = element_blank(),
  axis.line = element_line(size=.4))

ggplot(df, aes(x= a1, y= a2)) + 
  geom_point(aes(alpha=factor(a3), size = factor(a4))) + t1 + labs(x = "x label", y = "y label") +
  theme(legend.background = element_rect())

到目前为止，或多或少还不错。

我的问题是：

如何去除图例中的背景？ theme(legend.background = element_rect()) 由于某种原因不起作用...
如何修改我的图例headers？我通过这个例子想象：http://www.cookbook-r.com/Graphs/Legends_(ggplot2)/ 那应该是这样的：

scale_shape_discrete(name ="modified A4", breaks=c("1", "2"), labels = c("one","two")) 但我不知道如何让它工作？

我确定我完全误解了散点图中两个变量的显示，但我找不到更正它的方法？

谢谢！

Answer 1

根据@user20650 和@inscaven 的建议以及更多google 搜索，我希望更好地理解 ggplot 的组织方式以及如何生成我的情节：

# dummy data
a1<-c(seq(1,10,1))
a2<-c(seq(11,20,1))
a3<-c(rep(c(1,2),each = 5))
a4<-c(rep(c(5,10,15,20,25),2))

# create data frame 
df<-data.frame(a1,a2,a3,a4)

# set nice theme  
t1<-theme(        
  plot.background = element_blank(), 
  panel.grid.major = element_blank(), 
  panel.grid.minor = element_blank(), 
  panel.border = element_blank(), 
  panel.background = element_blank(),
  axis.line = element_line(size=.4))

# create scatter plot
ggplot(df, aes(x= a1, y= a2)) +                             # create basic plot
  geom_point(aes(size = factor(a4), colour = factor(a3))) + # colour has to be inside of aes !! (ASSIGNED = MAPPED)
  scale_colour_grey(name = "Set second\nline in title") +   # change title of 1st legend, change colours 
  scale_size_discrete(name = "Name by size") +              # change title of 2nd legend, size of point has been already assigned
  theme(legend.key = element_blank()) +                     # delete grey boxes around the legend
  labs(x = "x label", y = "y label") +                      # set labels on x and y  axes
  t1                                                        # add nice theme

这导致：

ggplot2：修改散点图 {ggplot2} 中两个因素的图例元素？

ggplot2: modify legend's elements for two factors in scatterplot {ggplot2}?

r

plot

ggplot2

legend-properties