Dataframe cust has Date-type column open.date. I wish to set up another
column, with (first day of) the quarter of open.date.
To be comprehensive (of course, improvement suggestions are welcome),
month = function(date)
{
return(as.numeric(format(date,"%m")))
}
first.day.of.month = function(date)
{
return(date + 1 - as.numeric(format(date,"%d")))
}
first.day.of.quarter = function(date)
{
t = seq.Date(first.day.of.month(date), by = "-1 month", length =
month(date) %% 3)
return(t[length(t)])
}
Now the main part,
> cust$open.quarter = apply(cust$open.date, 1, FUN = first.day.of.quarter)
Error in apply(cust$open.date, 1, FUN = first.day.of.quarter) :
dim(X) must have a positive length
> cust$open.quarter = tapply(cust$open.date, FUN = first.day.of.quarter)
Error in tapply(cust$open.date, FUN = first.day.of.quarter) :
element 1 is empty;
the part of the args list of 'is.list' being evaluated was:
(INDEX)
> cust$open.quarter = lapply(cust$open.date, FUN = first.day.of.quarter)
Error in prettyNum(.Internal(format(x, trim, digits, nsmall, width, 3L, :
invalid 'trim' argument
Can anyone suggest the right syntax?
Thank you.
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