Stefano,
How are you reading your data into R? If you are using a function like
read.table(), you may be able to inform R upon reading the data that -999
represents a missing value using an option like na.strings, for example:
read.table(file, na.strings="-999")
Otherwise, you can change the -999 to NA after creating the object my_array
using this:
my_array[my_array==-999] <- NA
Jean
On Tue, Apr 2, 2013 at 7:40 AM, Stefano Sofia <
stefano.so...@regione.marche.it> wrote:
> Dear R-users,
> suppose I have three dataframes like these
>
> df1:
> mydate min_temp
> 31032013 12
> 01042013 8
> 02042013 -999
>
> df2:
> mydate min_temp
> 31032013 10
> 01042013 11
> 02042013 14
>
> df3:
> mydate min_temp
> 31032013 4
> 01042013 3
> 02042013 5
>
> where -999 means that the temperature data is not available (at the moment
> I cannot change it to NA because I am not the db administrator);
> suppose also that oggi is 02042013.
>
> I need to create an array of all min_temp, having NA where min_temp is
> -999.
>
> my_array <- c(df1$min_temp[df1$mydate==oggi],
> df2$min_temp[df2$mydate==oggi], df3$min_temp[df3$mydate==oggi])
>
> creates
> (-999,14,5)
> while I need
> (NA,14,5)
>
> Can I do it directly while I create my_array, without using an external if
> statement?
>
> Thank you for your help
> Stefano Sofia
>
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