ggplot热图网格线格式geom_tile和geom_rect

Question

几天来我一直在创建热图，但无法使网格线的最终格式生效。请参见下面的代码和附图。我想做的是使用geom_tile（）使网格线沿热图的图块对齐，以便每个图块以盒装方式填充网格的内部。我可以使用geom_raster（）对齐网格线，但y轴标签在图块的顶部或底部打勾，但我需要在中心打勾（请参见红色突出显示），而且我也无法包装geom_raster磁贴周围有一条白线边框，因此颜色块在我的原始数据集中显得有些混乱。感谢格式化代码的帮助。非常感谢！

#The data set in long format 


y<- c("A","A","A","A","B","B","B","B","B","C","C","C","D","D","D")
    x<- c("2020-03-01","2020-03-15","2020-03-18","2020-03-18","2020-03-01","2020-03-01","2020-03-01","2020-03-01","2020-03-05","2020-03-06","2020-03-05","2020-03-05","2020-03-20","2020-03-20","2020-03-21")
    v<-data.frame(y,x)

#approach 1 using geom_tile but gridline does not align with borders of the tiles 
    v%>%
      count(y,x,drop=FALSE)%>%
      arrange(n)%>%
      ggplot(aes(x=x,y=fct_reorder(y,n,sum)))+
      geom_tile(aes(fill=n),color="white", size=0.25)

我曾尝试从another post运行类似的代码，但无法使其正常运行。我认为因为我的x变量是y变量的计数变量，所以无法格式化为在geom_rect（）中指定xmin和xmax的因子变量

#approach 2 using geom_raster but y-axis label can't tick at the center of tiles and there's no border around the tile to differentiate between tiles. 

v%>%
  count(y,x,drop=FALSE)%>%
  arrange(n)%>%
  ggplot()+
  geom_raster(aes(x=x,y=fct_reorder(y,n,sum),fill=n),hjust=0,vjust=0)

Answer 1

我认为保留刻度线并依次将网格线保持在适当位置是有意义的。为了仍然实现所需的功能，建议您将数据扩展为包括所有可能的组合，并将na.value设置为中性填充颜色：

# all possible combinations
all <- v %>% expand(y, x)

# join with all, n will be NA for obs. in all that are not present in v
v = v %>% group_by_at(vars(y, x)) %>% 
    summarize(n = n()) %>% right_join(all)

ggplot(data = v, 
       aes(x=x, y=fct_reorder(y,n, function(x) sum(x, na.rm = T))))+ # note that you must account for the NA values now 
geom_tile(aes(fill=n), color="white",
        size=0.25) +
scale_fill_continuous(na.value = 'grey90') +
scale_x_discrete(expand = c(0,0)) +
scale_y_discrete(expand = c(0,0))

Answer 2

这有点hack。我的方法将分类变量转换为数字，从而向绘图中添加与网格对齐的较小网格线。要摆脱主要的网格线，我只需使用theme()。缺点：中断和标签必须手动设置。

library(ggplot2)
library(dplyr)
library(forcats)

v1 <- v %>%
  count(y,x,drop=FALSE)%>%
  arrange(n) %>%
  mutate(y = fct_reorder(y, n, sum),
         y1 = as.integer(y),
         x = factor(x),
         x1 = as.integer(x))

labels_y <- levels(v1$y)
breaks_y <- seq_along(labels_y)

labels_x <- levels(v1$x)
breaks_x <- seq_along(labels_x)

ggplot(v1, aes(x=x1, y=y1))+
  geom_tile(aes(fill=n), color="white", size=0.25) + 
  scale_y_continuous(breaks = breaks_y, labels = labels_y) +
  scale_x_continuous(breaks = breaks_x, labels = labels_x) +
  theme(panel.grid.major = element_blank())

^{由reprex package（v0.3.0）于2020-05-23创建}

编辑：检查了较长的变量名

y<- c("John Doe","John Doe","John Doe","John Doe","Mary Jane","Mary Jane","Mary Jane","Mary Jane","Mary Jane","C","C","C","D","D","D")
x<- c("2020-03-01","2020-03-15","2020-03-18","2020-03-18","2020-03-01","2020-03-01","2020-03-01","2020-03-01","2020-03-05","2020-03-06","2020-03-05","2020-03-05","2020-03-20","2020-03-20","2020-03-21")
v<-data.frame(y,x)

^{由reprex package（v0.3.0）于2020-05-23创建}