[R] First value in a row

[Henrik Singmann]

Hi,

As Arun's idea was also my first idea let me pinpoint the problem of this solution.
It only works if the data in question (i.e., columns x1 to x3) follow the pattern of the example data insofar that the NAs form a triangle like structure. This is so because it loops over columns instead of rows and takes advantage of the triangle NA structure.

For example, slightly changing the data leads to a result that does not follow the description of Camilo seem to want:

dat1<-read.table(text="
Lat  Lon  x1  x2  x3
01    10  NA  NA  .1
01    11  .4  NA  .3
01    12  NA  .5  .6
",sep="",header=TRUE)

# correct answer from description would be .1, .4, .5

# arun's solution:
data.frame(dat1,NewColumn=rev(unlist(lapply(dat1[,3:5],function(x) x[!is.na(x)][1]))))

#  x3  x2  x1
# 0.1 0.5 0.4

# my solution:
apply(dat1[,-(1:2)], 1, function(x) x[!is.na(x)][1])

# [1] 0.1 0.4 0.5

So the question is, what you want and how the data looks.

Cheers,
Henrik


Am 24.07.2012 14:27, schrieb arun:
> Hi,
>
> Try this:
>
> dat1<-read.table(text="
> Lat  Lon  x1  x2  x3
> 01    10  NA  NA  .1
> 01    11  NA  .2  .3
> 01    12  .4  .5  .6
> ",sep="",header=TRUE)
>
> dat2<-dat1[,3:5]
>   dat3<-data.frame(dat1,NewColumn=rev(unlist(lapply(dat2,function(x) x[!is.na(x)][1]))))
> row.names(dat3)<-1:nrow(dat3)
>   dat3
>    Lat Lon  x1  x2  x3 NewColumn
> 1   1  10  NA  NA 0.1       0.1
> 2   1  11  NA 0.2 0.3       0.2
> 3   1  12 0.4 0.5 0.6       0.4
>
> A.K.
>
>
>
>
> ----- Original Message -----
> From: Camilo Mora <cmora at dal.ca>
> To: r-help at r-project.org
> Cc:
> Sent: Tuesday, July 24, 2012 2:48 AM
> Subject: [R] First value in a row
>
> Hi.
>
> This is likely a trivial problem but have not found a solution. Imagine the following dataframe:
>
> Lat   Lon  x1   x2  x3
> 01    10   NA   NA  .1
> 01    11   NA   .2  .3
> 01    12   .4   .5  .6
>
> I want to generate another column that consist of the first value in each row from columns x1 to x3. That is
>
> NewColumn
> .1
> .2
> .4
>
> Any input greatly appreciated,
>
> Thanks,
>
> Camilo
>
>
> Camilo Mora, Ph.D.
> Department of Geography, University of Hawaii
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>

-- 
Dipl. Psych. Henrik Singmann
PhD Student
Albert-Ludwigs-Universität Freiburg, Germany
http://www.psychologie.uni-freiburg.de/Members/singmann