R 在ggplot中，条形宽度或间距与x轴上的月份不一致

当月份在x轴上时，我很难在ggplot中使条的间距保持一致。这是我的密码：

date_field = c("2017-01-01",
               "2017-02-01",
               "2017-03-01",
               "2017-04-01",
               "2017-05-01",
               "2017-06-01",
               "2017-07-01",
               "2017-08-01",
               "2017-09-01",
               "2017-10-01",
               "2017-11-01",
               "2017-12-01",
               "2018-01-01",
               "2018-02-01",
               "2018-03-01",
               "2018-04-01",
               "2018-05-01",
               "2018-06-01",
               "2018-07-01",
               "2018-08-01",
               "2018-09-01",
               "2018-10-01",
               "2018-11-01",
               "2018-12-01")

totals_field = c(12,
                 23,
                 25,
                 24,
                 3,
                 76,
                 36,
                 55,
                 55,
                 34,
                 101,
                 30,
                 53,
                 26,
                 23,
                 23,
                 276,
                 37,
                 47,
                 75,
                 100,
                 150,
                 34,
                 30)

df <- data.frame(date_field, totals_field)

df$date_field <- as.Date(df$date_field)


df_plot <- ggplot(df) + 
  geom_bar(aes(x=date_field, y=totals_field, fill="red"), width=30, colour="white", stat="identity") + 
  theme(axis.text.x = element_text(angle = 90))+ theme(
  panel.background = element_rect(fill = "white",
                                colour = "white",
                                size = 0.5, linetype = "solid"),
  panel.grid.major = element_line(size = 0.5, linetype = 'solid',
                                colour = "white"), 
  panel.grid.minor = element_line(size = 0.25, linetype = 'solid',
                                colour = "white"),
  axis.line.y = element_line(color = "black", linetype = "solid"),
  axis.line.x = element_line(color = "black", linetype = "solid")
  ) + scale_x_continuous(expand = expansion(mult = c(0, 0))) + scale_y_continuous(expand = expansion(mult = c(0, 0)))+
  scale_x_date(date_labels = "%Y",date_breaks = "1 year")

df_plot

date\u field=c（“2017-01-01”，
"2017-02-01",
"2017-03-01",
"2017-04-01",
"2017-05-01",
"2017-06-01",
"2017-07-01",
"2017-08-01",
"2017-09-01",
"2017-10-01",
"2017-11-01",
"2017-12-01",
"2018-01-01",
"2018-02-01",
"2018-03-01",
"2018-04-01",
"2018-05-01",
"2018-06-01",
"2018-07-01",
"2018-08-01",
"2018-09-01",
"2018-10-01",
"2018-11-01",
"2018-12-01")
总计\字段=c（12，
23,
25,
24,
3.
76,
36,
55,
55,
34,
101,
30,
53,
26,
23,
23,
276,
37,
47,
75,
100,
150,
34,
30)
df可以显示您得到的输出。我没有发现该代码有任何不均匀的宽度。请查看我的编辑，包括图片。我认为这是ggplot下游的抗锯齿问题，我怀疑您正在windows机器上查看绘图窗口。我想如果您将“全局选项”中的图形设备更改为AGG，或者如果您使用
ggsave（…
我想在rMarkdown（HTML输出）中渲染绘图，那么它就会消失。我应该如何使用ggsave？实际上，它在rMarkdown中看起来很好。谢谢！