[R] Confusion with sapply

[Uwe Ligges]

Patnaik, Tirthankar wrote:
> Hi,
>  I have some confusion in applying a function over a column.
> 
> Here's my function. I just need to shift non-March month-ends to March
> month-ends. Initially I tried seq.dates, but one cannot give a negative
> increment (decrement) here.
> 
> return(as.Date(seq.dates(format(xdate,"%m/%d/%Y"),by="months",len=4)[4])
> )
> 
> Hence this simple function:
> 
>> mydate <- as.Date("2006-01-01")
>>
>> # Function to shift non-March company-reporting dates to March.
>> Set2March <- function(xdate){
> + # Combines non-March months into March months:
> + # Dec2006 -> Mar2007
> + # Mar2006 -> Mar2006
> + # Jun2006 -> Mar2006
> + # Sep2006 -> Mar2006
> + # VERY Specific code.
> +     Month <- format(xdate,"%m")
> +     wDate <- month.day.year(julian(xdate))
> +     if (Month=="12"){
> +         wDate$year <- wDate$year + 1
> +         wDate$month <- 3
> +     }else
> +     if (Month=="06"){
> +         wDate$month <- 3
> +     }else
> +     if (Month=="09"){
> +         wDate$month <- 3
> +         wDate$day <- wDate$day + 1
> +     }else warning ("No Changes made to the month, since month is not
> one of (6,9,12)")
> +     cDate <- chron(paste(wDate$month,wDate$day,wDate$year,sep="/"))
> +     return(as.Date(as.yearmon(as.Date(cDate,"%m/%d/%y")),frac=1))
> + }
>> Set2March(as.Date("2006-06-30"))
> [1] "2006-03-31"
>> Set2March(mydate)
> [1] "2006-01-31"
> Warning message:
> No Changes made to the month, since month is not one of (6,9,12) in:
> Set2March(mydate) 
> 
> Works well when I use it on a single date. Then I try it on a vector:
> 
> 
>> dc <- seq(as.Date("2006-01-01"),len=10, by="month")
>> dc
>  [1] "2006-01-01" "2006-02-01" "2006-03-01" "2006-04-01" "2006-05-01"
> "2006-06-01" "2006-07-01" "2006-08-01"
>  [9] "2006-09-01" "2006-10-01"
> 
> 
>> sapply(as.vector(dc),Set2March)
> Error in prettyNum(.Internal(format(x, trim, digits, nsmall, width, 3,
> : 
>         unimplemented type 'character' in 'asLogical'
> 
> What am I missing here? Shouldn't the function work with the sapply
> working on each entry?


1. Your code is not reproducible. Which packages are required? chron? 
But then, I still do not have as.yearmon()!
2. Why do you use as.vector() in the sapply call? I doubt it can work 
that way, because as.vector strips the attributes!


Uwe Ligges



> 
> TIA and best,
> -Tir
> 
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