extract first value from multiple columns

[leonedelman]

i am trying to do this in R. it is equivalent to the stata command

rowfirst

suppose i have four columns as shown below (T1, T2, T3, T4). I want to create a new column (TX) which contains for each row the first element in columns T1:T4.

ID T1 T2 T3 T4

A  0  2  4  5
B  .  .  6  5
C  .  8  6  1
D  .  .  .  9

ID TX
A   0
B   6
C   8
D   9

thank you everyone!!

 

[Dason]

Would those dots be stored as NA?

 

[leonedelman]

Would those dots be stored as NA?

Yes:yup: the dots below are stored as NA. thank you for your reply!

 

[pardha]

You can do some thing like this:

Assuming your data frame is called data

data$TX=as.vector(data[1,])

if in case no. of columns is not equal to no. of rows you can use below command it will replace empty values in TX with NA

iris$v1=as.vector(c(iris[1,],rep(NA,nrow(iris)-ncol(iris))))

 

[rogojel]

hi,
you would need to define a function to return the index of the first non NA in a vector, then use apply (or aggregate) on the data feame.

My shot at the function would be

NonNA= function(v){
return (match(0, 1:length(v)*is.na(v))
}

to return the first value instead of the index:

FirstNA= function(v){
ind= (match(0, 1:length(v)*is.na(v))
return(v[ind])
}

regards