如何显示在热图单元格中的数值单元格的值

Question

我试图创建一个热图来显示驱动每个单元格中颜色的值。如果一个单元格由于有5个观测值而呈深蓝色，我想看到该单元格中的数字5。

（目的是建立一个信用评级迁移矩阵，其中一个轴是今年的信用评级，另一个是去年的信用评级。输入是一个数据框，其中每行是一个公司的观察值，公司的信用以及去年的信用评级，矩阵显示哪些公司在两年期间信用评级稳定，评级较低，并且评级更高。

下面是数据和代码

require(ggplot2) 

# Create a dataframe mm where each row is one observation for one company, 
# the company's credit rating this year, and it credit rating last year. A company ID is 
# provided. 


mm<-data.frame(
    CompamyID = c(1:14), 
    CurrentYear =c("Aaa","Aa","B","Baa","C","Aaa","Aa","B","Baa","C","Aa","B","Baa","C"), 
    PreviousYear=c("Aaa","Aa","B","Baa","Aa","B","Baa","C","C","Aaa","Aa","B","Baa","C"), 
    Count=rep(1,14) 
) 

# Create heatmap and show the number of observations in each cell. 
# I have used label= # sum() for illustration but it is wrong. 

ggplot(data=mm, aes(x = mm$CurrentYear, y=mm$PreviousYear)) + 
    geom_bin2d() + 
    geom_text(aes(fill = mm$Count, label = sum(mm$Count)))+ 
    scale_x_discrete(limits =c("Aaa", "Aa", "A", "Baa", "Ba", "B", "Caa", "Ca", "C")) + 
    scale_y_discrete(limits=c("C","Ca","Caa","B","Ba", "Baa", "A", "Aa", "Aaa")) + 
    scale_fill_gradient2() + 
    theme(panel.grid.major = element_line(colour ="white", size = 0.5))+ 
    theme(panel.grid.minor = element_line(colour ="black", linetype ="dashed", size = 0.5)) + 
    theme(panel.background = element_rect(colour ="black", fill ="white",size = 1.0)) + 
    ggtitle("MIGRATION MATRIX USING geom_bin2d()") + 
    xlab("Current Year") + 
    ylab("Previous Year")   

Answer 1

我会用stat_bin2d所以ggplot2内部计算的计数，使他们的名字..count..下可用。

ggplot(data=mm, aes(x = mm$CurrentYear, y=mm$PreviousYear)) + 
    geom_bin2d() + 
    stat_bin2d(geom="text", aes(label=..count..))+ 
    scale_x_discrete(limits =c("Aaa", "Aa", "A", "Baa", "Ba", "B", "Caa", "Ca", "C")) + 
    scale_y_discrete(limits=c("C","Ca","Caa","B","Ba", "Baa", "A", "Aa", "Aaa")) + 
    scale_fill_gradient2() + 
    theme(panel.grid.major = element_line(colour ="white", size = 0.5))+ 
    theme(panel.grid.minor = element_line(colour ="black", linetype ="dashed", size = 0.5)) + 
    theme(panel.background = element_rect(colour ="black", fill ="white",size = 1.0)) + 
    ggtitle("MIGRATION MATRIX USING geom_bin2d()") + 
    xlab("Current Year") + 
    ylab("Previous Year") 

我希望有帮助。