# [R] simple problem, but not for me

Uwe Ligges ligges at statistik.uni-dortmund.de
Sat Mar 19 18:16:23 CET 2005

```alexbri wrote:

> Hello, I'm new in R and I want to do one thing that is very easy in excel, however, I cant do it in R.
>
> Suppose we have the data frame:
>
>
>
> data<- data.frame(A=c("a1","a2","a3","a4","a5"))
>
>
>
> I need to obtain another column in the same data frame (lets say B=c(b1,b2,b3,b4,b5) in the following way:
>
>
>
> b1=a1/(a1+a2+a3+a4+a5)
>
> b2=a2/(a2+a3+a4+a5)
>
> b3=a3/(a3+a4+a5)
>
> b4=a4/(a4+a5)
>
> b5=a5/a5

temp <- rev(data\$A)
data\$B <- rev(temp / cumsum(temp))

Uwe Ligges

>
>
> a1..a5 and b1...b5 are always numeric values
>
>
>
> (this is just an example, what I really want is apply this kind of formula to a much larger data frame)
>
>
>
> I think this is easy for those who are used to work in R (and I suppose there are many different ways), but I can make it in this moment, because I cannot leave behind, the "excel thinking way".
>
> I hope you understand my problem and please, help me soon.
>
>
>
> Alexandre
>
>
>
> alexbri at netcabo.pt
>
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```

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