r - 如何直方图星期几，并有字符串标签

Question

我有一个日期数据框(Date 对象)；见底部。
我试图将它们转换为星期几，然后绘制直方图，但理想情况下，标签是“星期一”...“星期日”(不是数字)

我有两个不同的问题:

很简单to convert a Date object to day-of-week ，但结果是字符串或数字，而不是对象。

当我得到直方图时，箱和标签是错误的(见下文)。

如果我使用 weekdays(dat) , 输出是字符串 ("Monday"...) 不能用于 hist() .

或者，如果我转换为数字数据，如何在 hist() 上获取字符串标签?

> dotw <- with( month.day.year(dat[,1]), day.of.week(month,day,year) )
> hist(xxx,labels=c('M','Tu','W','Th','F','Sa','Su'),col='black') # WTF?!
> hist(dotw,xlab=list('M','Tu','W','Th','F','Sa','Su'))

无法按预期进行标记。 0.5 宽度的垃圾箱有什么用？而且，如何防止周日-> 0 和周一-> 1 之间缺少间隙？理想情况下，列之间没有间隙。

我的数据看起来像:

> dat
  [1] "2010-04-02" "2010-04-06" "2010-04-09" "2010-04-10" "2010-04-14" "2010-04-15" "2010-04-19"
  [8] "2010-04-21" "2010-04-22" "2010-04-23" "2010-04-26" "2010-04-28" "2010-04-29" "2010-04-30"
 ...

> str(dat)
 Date[1:146], format: "2010-04-02" "2010-04-06" "2010-04-09" "2010-04-10" "2010-04-14" "2010-04-15" ...

> str(weekdays(dat))
 chr [1:146] "Friday" "Tuesday" "Friday" "Saturday" "Wednesday" "Thursday" "Monday" ...
> hist(weekdays(dat))
Error in hist.default(weekdays(dat)) : 'x' must be numeric

Answer 1

dat <- as.Date( c("2010-04-02", "2010-04-06", "2010-04-09", "2010-04-10", "2010-04-14", 
       "2010-04-15", "2010-04-19",   "2010-04-21", "2010-04-22", "2010-04-23","2010-04-24", 
        "2010-04-25", "2010-04-26", "2010-04-28", "2010-04-29", "2010-04-30"))
 dwka <- format(dat , "%a")
 dwka
# [1] "Fri" "Tue" "Fri" "Sat" "Wed" "Thu" "Mon"
#  [8] "Wed" "Thu" "Fri" "Sat" "Sun" "Mon" "Wed"
# [15] "Thu" "Fri"
dwkn <- as.numeric( format(dat , "%w") ) # numeric version
hist( dwkn , breaks= -.5+0:7, labels= unique(dwka[order(dwkn)]))