From: Rolf Turner <rolf_at_math.unb.ca>

Date: Sun 20 Mar 2005 - 04:38:52 EST

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Mar 20 04:43:58 2005

Date: Sun 20 Mar 2005 - 04:38:52 EST

> 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.
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Well, if you've deadened your brain by using Excel, no wonder.

> Suppose we have the data frame:

*>
**> data<- data.frame(A=c("a1","a2","a3","a4","a5"))
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Oh, for Pete's sake! This makes ``data'' (NOT a good name for an object!) into a data frame with a single column named ``A''. That column will be a factor with 5 entries (an 5 levels) with these levels being (the character strings) "a1","a2","a3","a4", and "a5". Nothing to do with what you actually want.

> I need to obtain another column in the same data frame (lets say

*> B=c(b1,b2,b3,b4,b5) in the following way:
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This would make B a ***vector*** equal to the concatenation of b1, ..., b5. Perhaps you mean: B <- cbind(b1,b2,b3,b4,b5)

> 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
**>
**> 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)
**>
*

You are very confused. Your notation and your use of the function c() are all wrong. If you are going to use R, get the basic syntax straight. You probably should be using matrices rather than data frames given that the entries are all numeric. Be that as it may, if A is a (numeric) matrix then B <- A/t(apply(A,1,function(x){rev(cumsum(x))})) will give what you appear to want. cheers, Rolf Turner rolf@math.unb.ca ______________________________________________R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Mar 20 04:43:58 2005

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