[R] interpreting date-related error message

[Toby Gass]

Hello, helpeRs,

I have a vector of numbers from 1-365 (days of the year) that I would 
like to convert to a date.  There are no NA's and no missing values. 
I did not insert leading zero's for numbers less than 100.

Using the syntax:

dat$doy.1 <- as.numeric(format(dat$doy, "%j" ))

I get the following error message:
  
Error in prettyNum(.Internal(format(x, trim, digits, nsmall, width, 
3L,  : 
  invalid 'trim' argument

.What is the error message telling me?
(Windows OS and R 2.11.1)


Thank you.

Toby