Why are there gaps on the heat map that cannot be deleted

General
1

Dear friends：
I am using ggplot2 to draw a heat map, but when the time variable is used as the horizontal axis, there is always a white gap as shown in the figure below. I have tried various methods but cannot delete it.
I earnestly request your guidance, thank you.

plotda <- xd[dtime<=as.Date('1962-3-1'),]
ggplot(plotda,aes(x=dtime,y=station,fill=severity))+
  geom_tile()+
  facet_grid(group~. )+
  scale_x_date(expand=expansion(mult=0,add=0),minor_breaks=NULL,date_labels='%Y%m')

image
image1419×832 92.3 KB

2

I'd try changing panel spacing to zero by adding

+ theme(panel.spacing = unit(0,"cm"))
3

Thank you very much for your answer, but multiple vertical gaps still exist.

4

for further assitance please provide a reprex