[R] Create New Column Inside Data Frame for Many Data Frames

[arun]

Hi,
 lapply(LETTERS[1:2],function(x) {x1<-get(x); x1$Rate<- ROC(x1$population);x1}) 
#[[1]]
 # population       Rate
#1        100         NA
#2        300  1.0986123
#3       5000  2.8134107
#4       2000 -0.9162907
#5        900 -0.7985077
#6       2500  1.0216512

#[[2]]
 # population       Rate
#1        200         NA
#2        300  0.4054651
#3       4000  2.5902672
#4       3000 -0.2876821
#5       2000 -0.4054651
#6        500 -1.3862944
#If it is for 26 letters
 lapply(LETTERS,function(x) {x1<-get(x); x1$Rate<- ROC(x1$population);x1})


A.K.



----- Original Message -----
From: "Sparks, John James" <jspark4 at uic.edu>
To: r-help at r-project.org
Cc: 
Sent: Sunday, April 14, 2013 1:19 PM
Subject: [R] Create New Column Inside Data Frame for Many Data Frames

Dear R Helpers,

I have a large number of data frames and I need to create a new column
inside each data frame.  Because there is a large number, I need to "loop"
through this, but I don't know the syntax of assigning a new column name
dynamically.

Below is a simple example of what I need to do.  Assume that I have to do
this for all 26 letters and you should see the form of the problem.

Any help would be much appreciated.  If more information is needed, please
let me know.

Many thanks.
--John Sparks



library(quantmod)
A <- data.frame(population=c(100, 300, 5000, 2000, 900, 2500))
A$Rate<-ROC(A["population"])

B <- data.frame(population=c(200, 300, 4000, 3000, 2000, 500))
B$Rate<-ROC(B["population"])

letters<-c("A","B")
length(letters)

#for (i in letters){
# HELP!
#}

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