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

arun smartpink111 at yahoo.com
Sun Apr 14 21:31:03 CEST 2013

```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.

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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