Hi
r-help-boun...@r-project.org napsal dne 22.06.2010 08:28:04:
> The following dataframe will illustrate the problem
>
>
DF<-data.frame(name=rep(1:5,each=2),x1=rep("A",10),x2=seq(10,19,by=1),x3=rep
> (NA,10),x4=seq(20,29,by=1))
> DF$x3[5]<-50
>
> # we have a data frame. we are interested in the columns x2,x3,x4 which
> contain sparse
> # values and many NA.
> DF
> name x1 x2 x3 x4
> 1 1 A 10 NA 20
> 2 1 A 11 NA 21
> 3 2 A 12 NA 22
> 4 2 A 13 NA 23
> 5 3 A 14 50 24
> 6 3 A 15 NA 25
> 7 4 A 16 NA 26
> 8 4 A 17 NA 27
> 9 5 A 18 NA 28
> 10 5 A 19 NA 29
>
> # we have a list of "target values that we want to search for in the
data
> frame
> # if the value is in the data frame we want to keep it there, otherwise,
> replace it with NA
>
> targets<-c(11,12,13,16,19,50,27,24,22,26)
> # so we apply a test by column to the last 3 columns using the "in" test
> # this gives us a mask of whether the data frame 'contains' elements in
the
> # target list
>
> mask<-apply(DF[,3:5],2, "%in%" ,targets)
> mask
>
> x2 x3 x4
> [1,] FALSE FALSE FALSE
> [2,] TRUE FALSE FALSE
> [3,] TRUE FALSE TRUE
> [4,] TRUE FALSE FALSE
> [5,] FALSE TRUE TRUE
> [6,] FALSE FALSE FALSE
> [7,] TRUE FALSE TRUE
> [8,] FALSE FALSE TRUE
> [9,] FALSE FALSE FALSE
> [10,] TRUE FALSE FALSE
>
> # and so DF[2,3] is equal to 11 and 11 is in the target list, so the
mask is
> True
> # now something like DF<- ifelse(mask==T,DF,NA) is CONCEPTUALLY what I
want
Data frames are quite clever in preserving their dimensions. I would do
mask=data.frame(a=TRUE, b=TRUE, !mask)
to add column 1 and 2
and
DF[mask]<-NA
Regards
Petr
> to do
> in the end I'd Like a result that looks like
>
> name x1 x2 x3 x4
> 1 1 A NA NA NA
> 2 1 A 11 NA NA
> 3 2 A 12 NA 22
> 4 2 A 13 NANA
> 5 3 A NA 50 24
> 6 3 A NA NA NA
> 7 4 A 16 NA 26
> 8 4 A NA NA 27
> 9 5 A NA NA NA
> 10 5 A 19 NA NA
>
> Ive tried forcing the DF and the mask into vectors so that ifelse()
would
> work
> and have tried "apply" using ifelse.. without much luck. any thoughts?
>
> [[alternative HTML version deleted]]
>
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