Question

I have a data-frame of dates (Date object); see bottom.
I’m trying to convert them to day-of-week and then draw a histogram, but ideally where the labels are ‘Monday’…’Sunday’ (not numeric)

I have two distinct problems:

1. It’s easy to convert a Date object to day-of-week, but the result is string or numeric, not an object.
2. When I get a histogram, the bins and labels are wrong (see below).

If I use weekdays(dat), the output is string (“Monday”…) which cannot be used in hist().

Alternatively, if I convert to numeric data, how to get string labels on hist()?

> 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'))

Does not work as intended for labeling. What’s with the 0.5-width bins? And also, how to prevent the lack of gap between Sunday->0 and Monday->1? Ideally, no gaps between columns.

My data looks like:

> 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)]))