[R] First value in a row

[Camilo Mora]

Hi Henrik and Arun,

I now understand the script you provided. Very smart solution I think.  
I wonder, however, if there is an alternative way as to count the last  
number in a row?.
For instance, considering the following dataframe

dat1<-read.table(text="
Lat  Lon  x1  x2  x3
01    12  .4  .5  .6
01    12  .2  .3  NA
01    11  .1  NA  NA
01    10  NA  NA  NA
",sep="",header=TRUE)

the last value (from left to right) should be:
.6
.3
.1
NA

NAs are always consecutive once they appear.

Thanks again,

Camilo


Camilo Mora, Ph.D.
Department of Geography, University of Hawaii
Currently available in Colombia
Phone:   Country code: 57
          Provider code: 313
          Phone 776 2282
          From the USA or Canada you have to dial 011 57 313 776 2282
http://www.soc.hawaii.edu/mora/



Quoting arun <smartpink111 at yahoo.com>:

> Hi Henrik,
>
> Thanks for testing it to a different dataset.  I didn't test it at  
> that time to multiple conditions.  Probably, apply is a better method.
>
>
> Anyway, you can still get the same result by doing this:
>
> 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)
> dat2<-data.frame(t(dat1[,3:5]))
> dat3<-data.frame(dat1,NewColumn=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 0.4  NA 0.3       0.4
> #3   1  12  NA 0.5 0.6       0.5
>
> #Now, to a slightly different dataset
> dat1<-read.table(text="
> Lat  Lon  x1  x2  x3
> 01    10  NA  NA  NA
> 01    11  NA  NA  .3
> 01    12  NA  .6   NA
> ",sep="",header=TRUE)
>  dat2<-data.frame(t(dat1[,3:5]))
>  dat3<-data.frame(dat1,NewColumn=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  NA        NA
> #2   1  11 NA  NA 0.3       0.3
> #3   1  12 NA 0.6  NA       0.6
>
>
> I hope this works well.
>
>
> A.K.
>
>
>
>
> ----- Original Message -----
> From: Henrik Singmann <henrik.singmann at psychologie.uni-freiburg.de>
> To: arun <smartpink111 at yahoo.com>
> Cc: Camilo Mora <cmora at dal.ca>; R help <r-help at r-project.org>
> Sent: Tuesday, July 24, 2012 10:18 AM
> Subject: Re: First value in a row
>
> 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
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> 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
>
>
>