On Tue, 2008-12-23 at 05:24 -0800, Tom La Bone wrote:
> I would like to add a column to the airquality dataset that contains the date
> 1950-01-01 in each row. This method does not appear to work:
>
> > attach(airquality)
> > data1 <- transform(airquality,Date=as.Date("1950-01-01"))
>
> Error in data.frame(list(Ozone = c(41L, 36L, 12L, 18L, NA, 28L, 23L, 19L, :
> arguments imply differing number of rows: 153, 1
>
> I can't decipher what the error message is trying to tell me. Any
> suggestions on how to do this?
It says that the two arguments have different numbers of observations.
The reason for which should now be pretty obvious as you provided a
single Date whereas airquality has 153 observations.
You did read ?transform , which points out this "problem"? ;-)
Anyway, don't assume R recycles everything if it is not of sufficient
length to match other arguments. In this case, repeat the date as many
times as there are rows in airquality:
> data(airquality)
> data1 <- transform(airquality, Date = rep(as.Date("1950-01-01"),
nrow(airquality)))
> head(data1)
Ozone Solar.R Wind Temp Month Day Date
1 41 190 7.4 67 5 1 1950-01-01
2 36 118 8.0 72 5 2 1950-01-01
3 12 149 12.6 74 5 3 1950-01-01
4 18 313 11.5 62 5 4 1950-01-01
5 NA NA 14.3 56 5 5 1950-01-01
6 28 NA 14.9 66 5 6 1950-01-01
Also, the attach(airquality) call in your example doesn't do anything
that affects your example so is redundant.
HTH
G
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Dr. Gavin Simpson [t] +44 (0)20 7679 0522
ECRC, UCL Geography, [f] +44 (0)20 7679 0565
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