如何使用Cassandra数据库（cql）和node.js的简单示例(Simple example of how to use the Cassandra database (cql) and node.js)

 我想，你想要reorder() 。 通常， reorder(x,y,FUN)根据将函数FUN应用于第二变量y的结果来改变因子x的级别的顺序。 在这种情况下，您可以使用FUN=length ，并且它对y使用什么并不重要。 
 
 设置数据（我选择修改概率以使结果更清晰）： 
 
set.seed(101)
df <- data.frame(Var1=as.factor(sample(c("AB", "BC", "CD", "DE", "EF"),
                            prob=c(0.1,0.5,0.2,0.05,0.15),
                                   1000, replace=TRUE)))
 
 基本情节（错误的顺序）： 
 
library(ggplot2)
print(g1 <- ggplot(df, aes(x=factor(1), fill=Var1))+
   geom_bar(width=1, colour="black")+
   coord_polar(theta="y")+
   theme_void())
 
  
 
 现在重新排序： 
 
df$Var1 <- reorder(df$Var1,df$Var1,FUN=length)
levels(df$Var1)
## [1] "DE" "AB" "EF" "CD" "BC"
 
 检查订单是否正确： 
 
sort(table(df$Var1))
##  DE  AB  EF  CD  BC 
##  46 105 163 189 497 
 
 打印新图（使用%+%粘贴新数据并使用guide_legend()翻转图例的顺序：也可以使用function(x) -length(x)作为FUN来更改guide_legend()的顺序第一名）。 
 
print(g1 %+% df + 
    scale_fill_discrete(guide=guide_legend(reverse=TRUE)))
 
  

You want reorder(), I think. In general reorder(x,y,FUN) changes the order of levels of a factor x according to the results of applying function FUN to a second variable y. In this case, you can use FUN=length, and it doesn't really matter what you use for y.
 
Set up data (I chose to modify the probabilities to make the result clearer):
 
set.seed(101)
df <- data.frame(Var1=as.factor(sample(c("AB", "BC", "CD", "DE", "EF"),
                            prob=c(0.1,0.5,0.2,0.05,0.15),
                                   1000, replace=TRUE)))
 
Basic plot (wrong order):
 
library(ggplot2)
print(g1 <- ggplot(df, aes(x=factor(1), fill=Var1))+
   geom_bar(width=1, colour="black")+
   coord_polar(theta="y")+
   theme_void())
 
 
Now reorder:
 
df$Var1 <- reorder(df$Var1,df$Var1,FUN=length)
levels(df$Var1)
## [1] "DE" "AB" "EF" "CD" "BC"
 
Check that the order is right:
 
sort(table(df$Var1))
##  DE  AB  EF  CD  BC 
##  46 105 163 189 497 
 
Print the new plot (stick in the new data with %+% and flip the order of the legend with guide_legend(): you could also use function(x) -length(x) as FUN to change the order of the levels in the first place).
 
print(g1 %+% df + 
    scale_fill_discrete(guide=guide_legend(reverse=TRUE)))