[R] problem with as.Date

[Duncan Murdoch]

On 11-10-22 4:26 PM, Martin Spindler wrote:
> Dear all,
>
> I would like to convert the first column of a dataframe to a date (original
> format: year (4 digits) and month (last 2 digits))
>
>> str(dat_FF)
> 'data.frame':	1022 obs. of  4 variables:
>   $ date : int  192607 192608 192609 192610 192611 192612 192701 192702
> 192703 192704 ...
>   $ Rm.Rf: num  2.69 2.52 0 -3.06 2.42 2.66 0 4.29 0.51 0.57 ...
>   $ SMB  : num  -2.49 -1.25 -1.38 -0.2 -0.34 -0.07 -0.11 0.35 -1.87 0.44 ...
>   $ HML  : num  -2.91 4.25 0.22 0.71 -0.4 -0.11 4.92 3.17 -2.92 1.33 ...
>
> But
>
>> dat_FF$date<- as.Date(as.character(dat_FF$date), format="%Y%m")
>
> delievers NAs:
>
>> str(dat_FF)
> 'data.frame':	1022 obs. of  4 variables:
>   $ date : Date, format: NA NA ...
>
> I am very grateful for hints! Thanks in advance!

I think you need to give a day.  For example, I get NA from

x <- "192607"
as.Date(x, format="%Y%m")

but it works with
x <- "19260701"
as.Date(x, format="%Y%m%d")

So I'd suggest pasting 01 (or whichever day you want) to the end of the 
as.character(dat_FF$date) strings.

Duncan Murdoch