R help - Apr 2010 - find the "next non-NA" value within each row of a data-frame

#I wish to find the "next non-NA" value within each row of a
data-frame.
#e.g. I have a data frame mydata. Rows 1, 2 & 3 have soem NA values.

mydata <- data.frame(matrix(seq(20*6), 20, 6))
mydata[1,3:5] <-  NA
mydata[2,2:3] <-  NA
mydata[2,5] <-  NA
mydata[3,6] <-  NA
mydata[1:3,]

#this loop accomplishes the task; I am tryign toi learn a "better" way

for(i in (ncol(mydata)-1):1 ){
mydata[,i] <- ifelse(is.na(mydata[,i])==TRUE,mydata[,i+1],mydata[,i])
}

mydata[1:3,]
#Thank you. I appreciate the help.



      
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If I understand correctly what you want (according to your loop),
you could use the na.locf function in pkg:zoo.

  library(zoo)
  mat <- t(apply(mydata, 1, na.locf, fromLast=TRUE, na.rm=FALSE))
  dat <- as.data.frame(mat) ## since apply returns a matrix

  -Peter Ehlers

On 2010-04-05 10:52, Anna Stevenson wrote:
> #I wish to find the "next non-NA" value within each row of a
data-frame.
> #e.g. I have a data frame mydata. Rows 1, 2&  3 have soem NA values.
>
> mydata<- data.frame(matrix(seq(20*6), 20, 6))
> mydata[1,3:5]<-  NA
> mydata[2,2:3]<-  NA
> mydata[2,5]<-  NA
> mydata[3,6]<-  NA
> mydata[1:3,]
>
> #this loop accomplishes the task; I am tryign toi learn a
"better" way
>
> for(i in (ncol(mydata)-1):1 ){
> mydata[,i]<- ifelse(is.na(mydata[,i])==TRUE,mydata[,i+1],mydata[,i])
> }
>
> mydata[1:3,]
> #Thank you. I appreciate the help.
>
>
>
>
> 	[[alternative HTML version deleted]]
>
>
>
>
> ______________________________________________
> 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.
-- 
Peter Ehlers
University of Calgary

Here is a slight simplification to the first line based on the fact
that na.locf works column by column:

mat <- t(na.locf(t(mydata), fromLast = TRUE, na.rm = FALSE))


On Mon, Apr 5, 2010 at 1:46 PM, Peter Ehlers <ehlers at ucalgary.ca>
wrote:
> If I understand correctly what you want (according to your loop),
> you could use the na.locf function in pkg:zoo.
>
> ?library(zoo)
> ?mat <- t(apply(mydata, 1, na.locf, fromLast=TRUE, na.rm=FALSE))
> ?dat <- as.data.frame(mat) ## since apply returns a matrix
>
> ?-Peter Ehlers
>
> On 2010-04-05 10:52, Anna Stevenson wrote:
>>
>> #I wish to find the "next non-NA" value within each row of a
data-frame.
>> #e.g. I have a data frame mydata. Rows 1, 2& ?3 have soem NA
values.
>>
>> mydata<- data.frame(matrix(seq(20*6), 20, 6))
>> mydata[1,3:5]<- ?NA
>> mydata[2,2:3]<- ?NA
>> mydata[2,5]<- ?NA
>> mydata[3,6]<- ?NA
>> mydata[1:3,]
>>
>> #this loop accomplishes the task; I am tryign toi learn a
"better" way
>>
>> for(i in (ncol(mydata)-1):1 ){
>> mydata[,i]<- ifelse(is.na(mydata[,i])==TRUE,mydata[,i+1],mydata[,i])
>> }
>>
>> mydata[1:3,]
>> #Thank you. I appreciate the help.
>>
>>
>>
>>
>> ? ? ? ?[[alternative HTML version deleted]]
>>
>>
>>
>>
>> ______________________________________________
>> 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.
>
> --
> Peter Ehlers
> University of Calgary
>
> ______________________________________________
> 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.
>