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

[jim holtman]

Here is another technique to use, especially if you have a long list
of replacement values:


> DF <- data.frame(number=c(1,4,7,3,11,16,14,17,20,19),data=c(1:10))
>
> # create a list of replacement values; if you have a lot and
> # you can create them automagically, then it is easier
> replace <- list(list(c(1, 7, 11, 16), "V1")
+               , list(c(4, 14, 20), "V2")
+               , list(c(3, 17, 19), "V3")
+               )
> for (i in replace){
+     DF$Station[DF$number %in% i[[1L]]] <- i[[2L]]
+ }
> DF
   number data Station
1       1    1      V1
2       4    2      V2
3       7    3      V1
4       3    4      V3
5      11    5      V1
6      16    6      V1
7      14    7      V2
8      17    8      V3
9      20    9      V2
10     19   10      V3


On Wed, Sep 26, 2012 at 6:49 AM, 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"))
>
> Could someone help me to finish this?
>
> Thank you very much!!!
>
>
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/create-new-column-in-a-DF-according-to-values-from-another-column-tp4644217.html
> Sent from the R help mailing list archive at Nabble.com.
>
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-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.