使用seq.Date作为stat_bin中的中断用于时间序列

Question

我试图使用stat_bin函数中的几个月观察数年的时间序列数据ggplot2.代码如下所示:

month.breaks<-seq.Date(from=min(afg$DateOccurred),to=max(afg$DateOccurred),by="month")  # All months, for breaks
report.region<-ggplot(afg,aes(x=DateOccurred))+stat_bin(aes(y=..density..,fill=Type),breaks=month.breaks)+facet_wrap(~Region)
print(report.region)

但是,当我运行print时,我收到以下错误:

Error in `+.Date`(left, right) : binary + is not defined for Date objects

如果我正确读取这个,则没有为Date对象定义加号运算符,因此无法执行这种类型的分箱操作？

Answer 1

我可以重现您的错误，如下所示：

> break.dates <- seq.Date(from=as.Date('2001-01-01'),
                          to=as.Date('2001-04-01'),
                          by="month") 
> break.dates
[1] "2001-01-01" "2001-02-01" "2001-03-01" "2001-04-01"
## add an offset, which increases the dates by a day
> break.dates + 1
[1] "2001-01-02" "2001-02-02" "2001-03-02" "2001-04-02"
## try to add two date objects together - this does not make sense!
> break.dates + break.dates
Error in `+.Date`(break.dates, break.dates) :
  binary + is not defined for Date objects

将两个日期加在一起是没有意义的，因为日期刻度上没有自然的“零”。然而，+运算符是Date在有意义的情况下为对象定义的。