[R] create new column in a DF according to values from another column

[Berend Hasselman]

On 26-09-2012, at 12:49, jeff6868 <geoffrey_klein at etu.u-bourgogne.fr> wrote:

> Hi everyone,
> 
> I have a small problem in my R-code.
> 
> Imagine this DF for example:
> 
> DF <- data.frame(number=c(1,4,7,3,11,16,14,17,20,19),data=c(1:10))
> 
> I would like to add a new column "Station" in this DF. This new column must
> be automatically filled with: "V1" or "V2" or "V3".
> The choice must be done on the numbers (1st column).
> 
> For example, I would like to have "V1" in the column "Station" in the rows
> where the numbers of the 1st column are: 1,7,11,16 ; then I would like to
> have "V2" in the rows where the numbers are: 4,14,20 and finally "V3" in the
> rows where the numbers are: 3,17,19.
> 
> I'm trying with "if" and something like this, but it's not working yet:
> # For "V1":
> if(DF$number %in% c(1,7,11,16)) {test$Station=="V1"}
> # For "V2":
> ... 
> 
> So my final DF should look like this:
> 
> FINALDF <- data.frame(number=c(1,4,7,3,11,16,14,17,20,19),data=c(1:10),
> Station=c("V1","V2","V1","V3","V1","V1","V2","V3","V2","V3"))
> 

DF[DF$number %in% c(1,7,11,16),"Station"] <- "V1"
DF[DF$number %in% c(4,14,20),"Station"] <- "V2"
DF[DF$number %in% c(3,17,19),"Station"] <- "V3"
DF

The Station column is of type character.
To make FINALDF identical you should add stringsAsFactors=FALSE to the arguments of data.frame.

Berend